diff --git a/src/conf.py b/src/conf.py
index 19f5b0711..33c88706e 100644
--- a/src/conf.py
+++ b/src/conf.py
@@ -134,6 +134,7 @@ def registerUserValue(group, name, value):
 
 class ValidNick(registry.String):
     """Value must be a valid IRC nick."""
+    __slots__ = ()
     def setValue(self, v):
         if not ircutils.isNick(v):
             self.error()
@@ -142,6 +143,7 @@ class ValidNick(registry.String):
 
 class ValidNickOrEmpty(ValidNick):
     """Value must be a valid IRC nick or empty."""
+    __slots__ = ()
     def setValue(self, v):
         if v != '' and not ircutils.isNick(v):
             self.error()
@@ -149,11 +151,13 @@ class ValidNickOrEmpty(ValidNick):
             registry.String.setValue(self, v)
 
 class ValidNicks(registry.SpaceSeparatedListOf):
+    __slots__ = ()
     Value = ValidNick
 
 class ValidNickAllowingPercentS(ValidNick):
     """Value must be a valid IRC nick, with the possible exception of a %s
     in it."""
+    __slots__ = ()
     def setValue(self, v):
         # If this works, it's a valid nick, aside from the %s.
         try:
@@ -164,10 +168,12 @@ class ValidNickAllowingPercentS(ValidNick):
             self.error()
 
 class ValidNicksAllowingPercentS(ValidNicks):
+    __slots__ = ()
     Value = ValidNickAllowingPercentS
 
 class ValidChannel(registry.String):
     """Value must be a valid IRC channel name."""
+    __slots__ = ('channel',)
     def setValue(self, v):
         self.channel = v
         if ',' in v:
@@ -194,6 +200,7 @@ class ValidChannel(registry.String):
 
 class ValidHostmask(registry.String):
     """Value must be a valid user hostmask."""
+    __slots__ = ()
     def setValue(self, v):
         if not ircutils.isUserHostmask(v):
             self.error()
@@ -219,6 +226,7 @@ registerGlobalValue(supybot, 'ident',
 # bots which are migrated from Supybot or an old version of Limnoria
 # (whose default value of supybot.user is the empty string).
 class VersionIfEmpty(registry.String):
+    __slots__ = ()
     def __call__(self):
         ret = registry.String.__call__(self)
         if not ret:
@@ -231,6 +239,7 @@ registerGlobalValue(supybot, 'user',
     will be generated if this is left empty.""")))
 
 class Networks(registry.SpaceSeparatedSetOfStrings):
+    __slots__ = ()
     List = ircutils.IrcSet
 
 registerGlobalValue(supybot, 'networks',
@@ -238,6 +247,7 @@ registerGlobalValue(supybot, 'networks',
              orderAlphabetically=True))
 
 class Servers(registry.SpaceSeparatedListOfStrings):
+    __slots__ = ()
     def normalize(self, s):
         if ':' not in s:
             s += ':6667'
@@ -262,6 +272,7 @@ class Servers(registry.SpaceSeparatedListOfStrings):
 
 class SocksProxy(registry.String):
     """Value must be a valid hostname:port string."""
+    __slots__ = ()
     def setValue(self, v):
         # TODO: improve checks
         if ':' not in v:
@@ -273,6 +284,7 @@ class SocksProxy(registry.String):
         super(SocksProxy, self).setValue(v)
 
 class SpaceSeparatedSetOfChannels(registry.SpaceSeparatedListOf):
+    __slots__ = ()
     sorted = True
     List = ircutils.IrcSet
     Value = ValidChannel
@@ -313,10 +325,12 @@ class SpaceSeparatedSetOfChannels(registry.SpaceSeparatedListOf):
             return None
 
 class ValidSaslMechanism(registry.OnlySomeStrings):
+    __slots__ = ()
     validStrings = ('ecdsa-nist256p-challenge', 'external', 'plain',
             'scram-sha-256')
 
 class SpaceSeparatedListOfSaslMechanisms(registry.SpaceSeparatedListOf):
+    __slots__ = ()
     Value = ValidSaslMechanism
 
 def registerNetwork(name, password='', ssl=True, sasl_username='',
@@ -554,6 +568,7 @@ registerChannelValue(supybot.reply, 'showSimpleSyntax',
 
 class ValidPrefixChars(registry.String):
     """Value must contain only ~!@#$%^&*()_-+=[{}]\\|'\";:,<.>/?"""
+    __slots__ = ()
     def setValue(self, v):
         if any([x not in '`~!@#$%^&*()_-+=[{}]\\|\'";:,<.>/?' for x in v]):
             self.error()
@@ -698,6 +713,7 @@ registerGroup(supybot, 'commands')
 
 class ValidQuotes(registry.Value):
     """Value must consist solely of \", ', and ` characters."""
+    __slots__ = ()
     def setValue(self, v):
         if [c for c in v if c not in '"`\'']:
             self.error()
@@ -722,6 +738,7 @@ registerGlobalValue(supybot.commands.nested, 'maximum',
     commands more nested than this.""")))
 
 class ValidBrackets(registry.OnlySomeStrings):
+    __slots__ = ()
     validStrings = ('', '[]', '<>', '{}', '()')
 
 registerChannelValue(supybot.commands.nested, 'brackets',
@@ -816,6 +833,7 @@ registerGlobalValue(supybot.drivers, 'poll',
     driver should block waiting for input.""")))
 
 class ValidDriverModule(registry.OnlySomeStrings):
+    __slots__ = ()
     validStrings = ('default', 'Socket', 'Twisted')
 
 registerGlobalValue(supybot.drivers, 'module',
@@ -836,6 +854,7 @@ registerGlobalValue(supybot.drivers, 'maxReconnectWait',
 # XXX This shouldn't make directories willy-nilly.  As it is now, if it's
 #     configured, it'll still make the default directories, I think.
 class Directory(registry.String):
+    __slots__ = ()
     def __call__(self):
         # ??? Should we perhaps always return an absolute path here?
         v = super(Directory, self).__call__()
@@ -857,6 +876,7 @@ class Directory(registry.String):
         return os.path.join(myself, filename)
 
 class DataFilename(registry.String):
+    __slots__ = ()
     def __call__(self):
         v = super(DataFilename, self).__call__()
         dataDir = supybot.directories.data()
@@ -867,6 +887,7 @@ class DataFilename(registry.String):
         return v
 
 class DataFilenameDirectory(DataFilename, Directory):
+    __slots__ = ()
     def __call__(self):
         v = DataFilename.__call__(self)
         v = Directory.__call__(self)
@@ -924,6 +945,7 @@ registerGlobalValue(supybot.plugins, 'alwaysLoadImportant',
 # supybot.databases.  For stuff relating to Supybot's databases (duh!)
 ###
 class Databases(registry.SpaceSeparatedListOfStrings):
+    __slots__ = ()
     def __call__(self):
         v = super(Databases, self).__call__()
         if not v:
@@ -976,6 +998,7 @@ registerGlobalValue(supybot.databases.channels, 'filename',
 # TODO This will need to do more in the future (such as making sure link.allow
 # will let the link occur), but for now let's just leave it as this.
 class ChannelSpecific(registry.Boolean):
+    __slots__ = ()
     def getChannelLink(self, channel):
         channelSpecific = supybot.databases.plugins.channelSpecific
         channels = [channel]
@@ -1029,6 +1052,7 @@ registerChannelValue(supybot.databases.plugins.channelSpecific.link, 'allow',
 
 
 class CDB(registry.Boolean):
+    __slots__ = ()
     def connect(self, filename):
         from . import cdb
         basename = os.path.basename(filename)
@@ -1069,6 +1093,7 @@ registerGroup(supybot, 'protocols')
 registerGroup(supybot.protocols, 'irc')
 
 class Banmask(registry.SpaceSeparatedSetOfStrings):
+    __slots__ = ('__parent', '__dict__') # __dict__ is needed to set __doc__
     validStrings = ('exact', 'nick', 'user', 'host')
     def __init__(self, *args, **kwargs):
         assert self.validStrings, 'There must be some valid strings.  ' \
@@ -1204,6 +1229,7 @@ registerGlobalValue(supybot.protocols.http, 'peekSize',
 
 class HttpProxy(registry.String):
     """Value must be a valid hostname:port string."""
+    __slots__ = ()
     def setValue(self, v):
         proxies = {}
         if v != "":
@@ -1242,6 +1268,7 @@ registerGroup(supybot.servers, 'http')
 
 class IP(registry.String):
     """Value must be a valid IP."""
+    __slots__ = ()
     def setValue(self, v):
         if v and not utils.net.isIP(v):
             self.error()
@@ -1249,6 +1276,7 @@ class IP(registry.String):
             registry.String.setValue(self, v)
 
 class ListOfIPs(registry.SpaceSeparatedListOfStrings):
+    __slots__ = ()
     Value = IP
 
 registerGlobalValue(supybot.servers.http, 'singleStack',
@@ -1295,6 +1323,7 @@ registerGlobalValue(supybot, 'externalIP',
 class SocketTimeout(registry.PositiveInteger):
     """Value must be an integer greater than supybot.drivers.poll and must be
     greater than or equal to 1."""
+    __slots__ = ()
     def setValue(self, v):
         if v < supybot.drivers.poll() or v < 1:
             self.error()
diff --git a/src/ircdb.py b/src/ircdb.py
index 0ada6b574..a16c9f129 100644
--- a/src/ircdb.py
+++ b/src/ircdb.py
@@ -108,6 +108,7 @@ def unWildcardHostmask(hostmask):
 _invert = invertCapability
 class CapabilitySet(set):
     """A subclass of set handling basic capability stuff."""
+    __slots__ = ('__parent',)
     def __init__(self, capabilities=()):
         self.__parent = super(CapabilitySet, self)
         self.__parent.__init__()
@@ -155,6 +156,7 @@ class CapabilitySet(set):
 antiOwner = makeAntiCapability('owner')
 class UserCapabilitySet(CapabilitySet):
     """A subclass of CapabilitySet to handle the owner capability correctly."""
+    __slots__ = ('__parent',)
     def __init__(self, *args, **kwargs):
         self.__parent = super(UserCapabilitySet, self)
         self.__parent.__init__(*args, **kwargs)
@@ -196,6 +198,8 @@ class UserCapabilitySet(CapabilitySet):
 
 class IrcUser(object):
     """This class holds the capabilities and authentications for a user."""
+    __slots__ = ('id', 'auth', 'name', 'ignore', 'secure', 'hashed',
+            'password', 'capabilities', 'hostmasks', 'nicks', 'gpgkeys')
     def __init__(self, ignore=False, password='', name='',
                  capabilities=(), hostmasks=None, nicks=None,
                  secure=False, hashed=False):
@@ -368,6 +372,8 @@ class IrcUser(object):
 
 class IrcChannel(object):
     """This class holds the capabilities, bans, and ignores of a channel."""
+    __slots__ = ('defaultAllow', 'expiredBans', 'bans', 'ignores', 'silences',
+            'exceptions', 'capabilities', 'lobotomized')
     defaultOff = ('op', 'halfop', 'voice', 'protected')
     def __init__(self, bans=None, silences=None, exceptions=None, ignores=None,
                  capabilities=None, lobotomized=False, defaultAllow=True):
@@ -491,10 +497,12 @@ class IrcChannel(object):
 
 
 class Creator(object):
+    __slots__ = ()
     def badCommand(self, command, rest, lineno):
         raise ValueError('Invalid command on line %s: %s' % (lineno, command))
 
 class IrcUserCreator(Creator):
+    __slots__ = ('users')
     u = None
     def __init__(self, users):
         if self.u is None:
@@ -563,6 +571,7 @@ class IrcUserCreator(Creator):
             IrcUserCreator.u = None
 
 class IrcChannelCreator(Creator):
+    __slots__ = ('c', 'channels', 'hadChannel')
     name = None
     def __init__(self, channels):
         self.c = IrcChannel()
@@ -611,6 +620,8 @@ class DuplicateHostmask(ValueError):
 
 class UsersDictionary(utils.IterableMap):
     """A simple serialized-to-file User Database."""
+    __slots__ = ('noFlush', 'filename', 'users', '_nameCache',
+            '_hostmaskCache')
     def __init__(self):
         self.noFlush = False
         self.filename = None
@@ -821,6 +832,7 @@ class UsersDictionary(utils.IterableMap):
 
 
 class ChannelsDictionary(utils.IterableMap):
+    __slots__ = ('noFlush', 'filename', 'channels')
     def __init__(self):
         self.noFlush = False
         self.filename = None
@@ -897,6 +909,7 @@ class ChannelsDictionary(utils.IterableMap):
 
 
 class IgnoresDB(object):
+    __slots__ = ('filename', 'hostmasks')
     def __init__(self):
         self.filename = None
         self.hostmasks = {}
@@ -1145,9 +1158,11 @@ def checkCapabilities(hostmask, capabilities, requireAll=False):
 ###
 
 class SpaceSeparatedListOfCapabilities(registry.SpaceSeparatedListOfStrings):
+    __slots__ = ()
     List = CapabilitySet
 
 class DefaultCapabilities(SpaceSeparatedListOfCapabilities):
+    __slots__ = ()
     # We use a keyword argument trick here to prevent eval'ing of code that
     # changes allowDefaultOwner from affecting this.  It's not perfect, but
     # it's still an improvement, raising the bar for potential crackers.
diff --git a/src/registry.py b/src/registry.py
index 56d9cb7a6..8c74dd56f 100644
--- a/src/registry.py
+++ b/src/registry.py
@@ -191,6 +191,8 @@ def join(names):
 
 class Group(object):
     """A group; it doesn't hold a value unless handled by a subclass."""
+    __slots__ = ('_help', '_name', '_added', '_children', '_lastModified',
+            '_private', '_supplyDefault', '_orderAlphabetically', '_wasSet')
     def __init__(self, help='', supplyDefault=False,
                  orderAlphabetically=True, private=False):
         self._help = utils.str.normalizeWhitespace(help)
@@ -201,7 +203,6 @@ class Group(object):
         self._private = private
         self._supplyDefault = supplyDefault
         self._orderAlphabetically = orderAlphabetically
-        OriginalClass = self.__class__
         self._wasSet = True
 
     def __call__(self):
@@ -326,6 +327,8 @@ class _NoValueGiven:
 class Value(Group):
     """Invalid registry value.  If you're getting this message, report it,
     because we forgot to put a proper help string here."""
+    __slots__ = ('__parent', '_default', '_showDefault', '_help', '_callbacks',
+            'value', 'channelValue', '_opSettable')
     def __init__(self, default, help, setDefault=True,
                  showDefault=True, **kwargs):
         self.__parent = super(Value, self)
@@ -421,6 +424,7 @@ class Value(Group):
 
 class Boolean(Value):
     """Value must be either True or False (or On or Off)."""
+    __slots__ = ()
     errormsg = _('Value must be either True or False (or On or Off), not %r.')
     def set(self, s):
         try:
@@ -437,6 +441,7 @@ class Boolean(Value):
 
 class Integer(Value):
     """Value must be an integer."""
+    __slots__ = ()
     errormsg = _('Value must be an integer, not %r.')
     def set(self, s):
         try:
@@ -446,6 +451,7 @@ class Integer(Value):
 
 class NonNegativeInteger(Integer):
     """Value must be a non-negative integer."""
+    __slots__ = ()
     errormsg = _('Value must be a non-negative integer, not %r.')
     def setValue(self, v):
         if v < 0:
@@ -454,6 +460,7 @@ class NonNegativeInteger(Integer):
 
 class PositiveInteger(NonNegativeInteger):
     """Value must be positive (non-zero) integer."""
+    __slots__ = ()
     errormsg = _('Value must be positive (non-zero) integer, not %r.')
     def setValue(self, v):
         if not v:
@@ -462,6 +469,7 @@ class PositiveInteger(NonNegativeInteger):
 
 class Float(Value):
     """Value must be a floating-point number."""
+    __slots__ = ()
     errormsg = _('Value must be a floating-point number, not %r.')
     def set(self, s):
         try:
@@ -477,6 +485,7 @@ class Float(Value):
 
 class PositiveFloat(Float):
     """Value must be a floating-point number greater than zero."""
+    __slots__ = ()
     errormsg = _('Value must be a floating-point number greater than zero, '
             'not %r.')
     def setValue(self, v):
@@ -487,6 +496,7 @@ class PositiveFloat(Float):
 
 class Probability(Float):
     """Value must be a floating point number in the range [0, 1]."""
+    __slots__ = ('__parent',)
     errormsg = _('Value must be a floating point number in the range [0, 1], '
             'not %r.')
     def __init__(self, *args, **kwargs):
@@ -501,6 +511,7 @@ class Probability(Float):
 
 class String(Value):
     """Value is not a valid Python string."""
+    __slots__ = ()
     errormsg = _('Value should be a valid Python string, not %r.')
     def set(self, s):
         v = s
@@ -527,6 +538,8 @@ class String(Value):
         return s
 
 class OnlySomeStrings(String):
+    __slots__ = ('__parent', '__dict__') # unfortunately, __dict__ is needed
+                                         # to set __doc__.
     validStrings = ()
     def __init__(self, *args, **kwargs):
         assert self.validStrings, 'There must be some valid strings.  ' \
@@ -559,6 +572,7 @@ class OnlySomeStrings(String):
             self.error(v)
 
 class NormalizedString(String):
+    __slots__ = ('__parent')
     def __init__(self, default, *args, **kwargs):
         default = self.normalize(default)
         self.__parent = super(NormalizedString, self)
@@ -591,6 +605,7 @@ class NormalizedString(String):
         return ret
 
 class StringSurroundedBySpaces(String):
+    __slots__ = ()
     def setValue(self, v):
         if v and v.lstrip() == v:
             v= ' ' + v
@@ -599,6 +614,7 @@ class StringSurroundedBySpaces(String):
         super(StringSurroundedBySpaces, self).setValue(v)
 
 class StringWithSpaceOnRight(String):
+    __slots__ = ()
     def setValue(self, v):
         if v and v.rstrip() == v:
             v += ' '
@@ -606,6 +622,7 @@ class StringWithSpaceOnRight(String):
 
 class Regexp(Value):
     """Value must be a valid regular expression."""
+    __slots__ = ('sr', 'value', '__parent')
     errormsg = _('Value must be a valid regular expression, not %r.')
     def __init__(self, *args, **kwargs):
         kwargs['setDefault'] = False
@@ -645,6 +662,7 @@ class Regexp(Value):
         return self.sr
 
 class SeparatedListOf(Value):
+    __slots__ = ()
     List = list
     Value = Value
     sorted = False
@@ -681,23 +699,28 @@ class SeparatedListOf(Value):
             return ' '
 
 class SpaceSeparatedListOf(SeparatedListOf):
+    __slots__ = ()
     def splitter(self, s):
         return s.split()
     joiner = ' '.join
 
 class SpaceSeparatedListOfStrings(SpaceSeparatedListOf):
+    __slots__ = ()
     Value = String
 
 class SpaceSeparatedSetOfStrings(SpaceSeparatedListOfStrings):
+    __slots__ = ()
     List = set
 
 class CommaSeparatedListOfStrings(SeparatedListOf):
+    __slots__ = ()
     Value = String
     def splitter(self, s):
         return re.split(r'\s*,\s*', s)
     joiner = ', '.join
 
 class CommaSeparatedSetOfStrings(SeparatedListOf):
+    __slots__ = ()
     List = set
     Value = String
     def splitter(self, s):
@@ -705,6 +728,7 @@ class CommaSeparatedSetOfStrings(SeparatedListOf):
     joiner = ', '.join
 
 class TemplatedString(String):
+    __slots__ = ()
     requiredTemplates = []
     def __init__(self, *args, **kwargs):
         assert self.requiredTemplates, \
@@ -721,6 +745,7 @@ class TemplatedString(String):
             self.error(v)
 
 class Json(String):
+    __slots__ = ()
     # Json-serializable data
     def set(self, v):
         self.setValue(json.loads(v))