diff --git a/trytond/CHANGELOG b/trytond/CHANGELOG
index ff69750a8d..42a8013af6 100644
--- a/trytond/CHANGELOG
+++ b/trytond/CHANGELOG
@@ -1,3 +1,4 @@
+* Add chat backend
 * Transaction.check_warnings is now a directory mapping the key to the warnings
 * Store target of field as relation
 * Remove support for Python 3.8
diff --git a/trytond/trytond/ir/__init__.py b/trytond/trytond/ir/__init__.py
index cf104fb2b5..179ef11154 100644
--- a/trytond/trytond/ir/__init__.py
+++ b/trytond/trytond/ir/__init__.py
@@ -3,9 +3,9 @@
 from trytond.pool import Pool
 
 from . import (
-    action, attachment, avatar, cache, calendar_, configuration, cron, date,
-    email_, error, export, lang, message, model, module, note, queue_, routes,
-    rule, sequence, session, translation, trigger, ui)
+    action, attachment, avatar, cache, calendar_, chat, configuration, cron,
+    date, email_, error, export, lang, message, model, module, note, queue_,
+    routes, rule, sequence, session, translation, trigger, ui)
 
 __all__ = ['register', 'routes']
 
@@ -96,6 +96,9 @@ def register():
         email_.EmailTemplate,
         email_.EmailTemplate_Report,
         error.Error,
+        chat.Channel,
+        chat.Follower,
+        chat.Message,
         module='ir', type_='model')
     Pool.register(
         translation.TranslationSet,
diff --git a/trytond/trytond/ir/chat.py b/trytond/trytond/ir/chat.py
new file mode 100644
index 0000000000..6b896e3579
--- /dev/null
+++ b/trytond/trytond/ir/chat.py
@@ -0,0 +1,271 @@
+# This file is part of Tryton.  The COPYRIGHT file at the top level of
+# this repository contains the full copyright notices and license terms.
+
+from sql import Null
+from sql.conditionals import NullIf
+
+from trytond.i18n import gettext
+from trytond.model import ChatMixin, Check, ModelSQL, Unique, fields
+from trytond.model.exceptions import ValidationError
+from trytond.pool import Pool
+from trytond.rpc import RPC
+from trytond.tools.email_ import (
+    EmailNotValidError, normalize_email, validate_email)
+from trytond.transaction import Transaction
+
+
+class InvalidEMailError(ValidationError):
+    pass
+
+
+class Channel(ModelSQL):
+    "Chat Channel"
+    __name__ = 'ir.chat.channel'
+
+    resource = fields.Reference(
+        "Resource", selection='get_models', required=True)
+    followers = fields.One2Many(
+        'ir.chat.follower', 'channel', "Followers")
+
+    @classmethod
+    def __setup__(cls):
+        super().__setup__()
+        t = cls.__table__()
+        cls._sql_constraints += [
+            ('resource_unique', Unique(t, t.resource),
+                'ir.msg_chat_channel_resource_unique'),
+            ]
+        cls.__rpc__.update(
+            subscribe=RPC(readonly=False),
+            unsubscribe=RPC(readonly=False),
+            subscribe_email=RPC(readonly=False),
+            unsubscribe_email=RPC(readonly=False),
+            post=RPC(readonly=False, result=int),
+            get_models=RPC(),
+            get=RPC(),
+            )
+
+    @classmethod
+    def get_models(cls):
+        pool = Pool()
+        Model = pool.get('ir.model')
+        return [
+            (m, n) for m, n in Model.get_name_items()
+            if issubclass(pool.get(m), ChatMixin)]
+
+    @classmethod
+    def check_access(cls, resource):
+        pool = Pool()
+        ModelAccess = pool.get('ir.model.access')
+        model, id_ = resource.split(',')
+        ModelAccess.check(model, mode='read')
+        # TODO check record rule
+
+    @classmethod
+    def _get_channel(cls, resource):
+        cls.check_access(resource)
+        channels = cls.search([
+                ('resource', '=', str(resource)),
+                ])
+        if channels:
+            channel, = channels
+        else:
+            channel = cls(resource=str(resource))
+            channel.save()
+        return channel
+
+    @classmethod
+    def subscribe(cls, resource, username):
+        pool = Pool()
+        Follower = pool.get('ir.chat.follower')
+        User = pool.get('res.user')
+        user, = User.search([
+                ('login', '=', username),
+                ])
+        channel = cls._get_channel(resource)
+        Follower.add_user(channel, user)
+
+    @classmethod
+    def unsubscribe(cls, resource):
+        pool = Pool()
+        Follower = pool.get('ir.chat.follower')
+        User = pool.get('res.user')
+        user = User(Transaction().user)
+        channel = cls._get_channel(resource)
+        Follower.remove_user(channel, user)
+
+    @classmethod
+    def subscribe_email(cls, resource, email):
+        pool = Pool()
+        Follower = pool.get('ir.chat.follower')
+        channel = cls._get_channel(resource)
+        Follower.add_email(channel, email)
+
+    @classmethod
+    def unsubscribe_email(cls, resource, email):
+        pool = Pool()
+        Follower = pool.get('ir.chat.follower')
+        channel = cls._get_channel(resource)
+        Follower.remove_email(channel, email)
+
+    @classmethod
+    def post(cls, resource, content, audience='internal'):
+        pool = Pool()
+        Message = pool.get('ir.chat.message')
+        User = pool.get('res.user')
+        user = User(Transaction().user)
+        channel = cls._get_channel(resource)
+        message = Message(
+            channel=channel,
+            user=user,
+            content=content,
+            audience=audience)
+        message.save()
+        return message
+
+    @classmethod
+    def get(cls, resource, before=None, after=None):
+        pool = Pool()
+        Message = pool.get('ir.chat.message')
+        cls.check_access(resource)
+        domain = [
+            ('channel.resource', '=', resource),
+            ]
+        if before is not None:
+            domain.append(('id', '<', int(before)))
+        if after is not None:
+            domain.append(('id', '>', int(after)))
+        messages = Message.search(domain)
+        return [m.as_dict() for m in messages]
+
+
+class AuthorMixin:
+    __slots__ = ()
+
+    author = fields.Function(fields.Char("Author"), 'on_change_with_author')
+    user = fields.Many2One('res.user', "User", ondelete='CASCADE')
+    email = fields.Char("Email")
+
+    @classmethod
+    def __setup__(cls):
+        super().__setup__()
+        t = cls.__table__()
+        cls._sql_constraints += [
+            ('check_user_or_email',
+                Check(t,
+                    ((t.user == Null) & (NullIf(t.email, '') != Null))
+                    | ((t.user != Null) & (NullIf(t.email, '') == Null))),
+                'ir.msg_chat_user_or_email'),
+            ]
+
+    @classmethod
+    def validate_fields(cls, authors, field_names):
+        super().validate_fields(authors, field_names)
+        cls.check_valid_email(authors, field_names)
+
+    @classmethod
+    def check_valid_email(cls, authors, field_names=None):
+        if field_names and 'email' not in field_names:
+            return
+        for author in authors:
+            if author.email:
+                try:
+                    validate_email(author.email)
+                except EmailNotValidError as e:
+                    raise InvalidEMailError(gettext(
+                            'ir.msg_chat_author_email_invalid',
+                            email=author.email),
+                        str(e)) from e
+
+    @fields.depends('user', 'email')
+    def on_change_with_author(self, name=None):
+        if self.user:
+            return self.user.name
+        elif self.email:
+            return self.email
+
+    @property
+    def avatar_url(self):
+        if self.user:
+            return self.user.avatar_url
+
+
+class Follower(AuthorMixin, ModelSQL):
+    "Chat Follower"
+    __name__ = 'ir.chat.follower'
+
+    channel = fields.Many2One(
+        'ir.chat.channel', "Channel", required=True, ondelete='CASCADE')
+
+    @classmethod
+    def __setup__(cls):
+        super().__setup__()
+        t = cls.__table__()
+        cls._sql_constraints += [
+            ('channel_user_unique',
+                Unique(t, t.channel, t.user),
+                'ir.msg_chat_follower_channel_user_unique'),
+            ('channel_email_unique',
+                Unique(t, t.channel, t.email),
+                'ir.msg_chat_follower_channel_email_unique'),
+            ]
+
+    @classmethod
+    def add_user(cls, channel, user):
+        if not cls.search([
+                    ('channel', '=', channel),
+                    ('user', '=', user),
+                    ]):
+            cls(channel=channel, user=user).save()
+
+    @classmethod
+    def remove_user(cls, channel, user):
+        cls.delete(cls.search([
+                    ('channel', '=', channel),
+                    ('user', '=', user),
+                    ]))
+
+    @classmethod
+    def add_email(cls, channel, email):
+        email = normalize_email(email)
+        if not cls.search([
+                    ('channel', '=', channel),
+                    ('email', '=', email),
+                    ]):
+            cls(channel=channel, email=email).save()
+
+    @classmethod
+    def remove_email(cls, channel, email):
+        email = normalize_email(email)
+        cls.delete(cls.search([
+                    ('channel', '=', channel),
+                    ('email', '=', email),
+                    ]))
+
+
+class Message(AuthorMixin, ModelSQL):
+    "Chat Message"
+    __name__ = 'ir.chat.message'
+
+    channel = fields.Many2One(
+        'ir.chat.channel', "Channel", required=True, ondelete='RESTRICT')
+    content = fields.Text("Content", required=True)
+    audience = fields.Selection([
+            ('internal', "Internal"),
+            ('public', "Public"),
+            ], "Audience", required=True)
+
+    @classmethod
+    def default_audience(cls):
+        return 'public'
+
+    def as_dict(self):
+        return {
+            'id': self.id,
+            'timestamp': self.create_date,
+            'user': self.user.id if self.user else None,
+            'author': self.author,
+            'avatar_url': self.avatar_url,
+            'content': self.content,
+            'audience': self.audience,
+            }
diff --git a/trytond/trytond/ir/exceptions.py b/trytond/trytond/ir/exceptions.py
index e73fe5bf92..5db5ed512c 100644
--- a/trytond/trytond/ir/exceptions.py
+++ b/trytond/trytond/ir/exceptions.py
@@ -1,6 +1,7 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
 
+from .chat import InvalidEMailError as ChatInvalidEmailError
 from .lang import DateError as LanguageDateError
 from .lang import DeleteDefaultError as LanguageDeleteDefaultError
 from .lang import GroupingError as LanguageGroupingError
@@ -13,6 +14,7 @@ from .translation import OverriddenError as TranslationOverriddenError
 from .trigger import ConditionError as TriggerConditionError
 
 __all__ = [
+    ChatInvalidEmailError,
     DeactivateDependencyError,
     LanguageDateError,
     LanguageDeleteDefaultError,
diff --git a/trytond/trytond/ir/message.xml b/trytond/trytond/ir/message.xml
index 8c88fac4f2..13228c20d7 100644
--- a/trytond/trytond/ir/message.xml
+++ b/trytond/trytond/ir/message.xml
@@ -454,5 +454,20 @@ this repository contains the full copyright notices and license terms. -->
         <record model="ir.message" id="msg_model_data_db_id_model_unique">
             <field name="text">The database ID must be unique per model.</field>
         </record>
+        <record model="ir.message" id="msg_chat_channel_resource_unique">
+            <field name="text">Only one channel per resource is allowed.</field>
+        </record>
+        <record model="ir.message" id="msg_chat_user_or_email">
+            <field name="text">Only user or email can be filled.</field>
+        </record>
+        <record model="ir.message" id="msg_chat_follower_channel_user_unique">
+            <field name="text">A user can follow a channel only once.</field>
+        </record>
+        <record model="ir.message" id="msg_chat_follower_channel_email_unique">
+            <field name="text">An email can follow a channel only once.</field>
+        </record>
+        <record model="ir.message" id="msg_chat_author_email_invalid">
+            <field name="text">The email address "%(email)s" is not valid.</field>
+        </record>
     </data>
 </tryton>
diff --git a/trytond/trytond/model/__init__.py b/trytond/trytond/model/__init__.py
index 708c659325..bc2fbed599 100644
--- a/trytond/trytond/model/__init__.py
+++ b/trytond/trytond/model/__init__.py
@@ -2,6 +2,7 @@
 # this repository contains the full copyright notices and license terms.
 from .active import DeactivableMixin
 from .avatar import avatar_mixin
+from .chat import ChatMixin
 from .descriptors import dualmethod
 from .dictschema import DictSchemaMixin
 from .digits import DigitsMixin
@@ -23,4 +24,4 @@ __all__ = ['Model', 'ModelView', 'ModelStorage', 'ModelSingleton', 'ModelSQL',
     'Workflow', 'DictSchemaMixin', 'MatchMixin', 'UnionMixin', 'dualmethod',
     'MultiValueMixin', 'ValueMixin', 'SymbolMixin', 'DigitsMixin',
     'EvalEnvironment', 'sequence_ordered', 'sort', 'DeactivableMixin', 'tree',
-    'sum_tree', 'avatar_mixin']
+    'sum_tree', 'avatar_mixin', 'ChatMixin']
diff --git a/trytond/trytond/model/chat.py b/trytond/trytond/model/chat.py
new file mode 100644
index 0000000000..069f2de7c6
--- /dev/null
+++ b/trytond/trytond/model/chat.py
@@ -0,0 +1,6 @@
+# This file is part of Tryton.  The COPYRIGHT file at the top level of
+# this repository contains the full copyright notices and license terms.
+
+
+class ChatMixin:
+    __slots__ = ()