diff --git a/activities/migrations/0017_post_language.py b/activities/migrations/0017_post_language.py
new file mode 100644
index 000000000..4774d0d77
--- /dev/null
+++ b/activities/migrations/0017_post_language.py
@@ -0,0 +1,18 @@
+# Generated by Django 4.2.1 on 2023-05-15 09:26
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("activities", "0016_index_together_migration"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="post",
+            name="language",
+            field=models.CharField(default=""),
+        ),
+    ]
diff --git a/activities/models/post.py b/activities/models/post.py
index 045233e99..6138ad652 100644
--- a/activities/models/post.py
+++ b/activities/models/post.py
@@ -31,6 +31,7 @@
 from core.ld import (
     canonicalise,
     format_ld_date,
+    get_language,
     get_list,
     get_value_or_map,
     parse_ld_date,
@@ -252,6 +253,9 @@ class Types(models.TextChoices):
     # The main (HTML) content
     content = models.TextField()
 
+    # The language of the content
+    language = models.CharField(default="")
+
     type = models.CharField(
         max_length=20,
         choices=Types.choices,
@@ -474,6 +478,7 @@ def create_local(
         reply_to: Optional["Post"] = None,
         attachments: list | None = None,
         question: dict | None = None,
+        language: str | None = None,
     ) -> "Post":
         with transaction.atomic():
             # Find mentions in this post
@@ -492,6 +497,9 @@ def create_local(
                 sorted([tag[: Hashtag.MAXIMUM_LENGTH] for tag in parser.hashtags])
                 or None
             )
+            if language is None or language == "":
+                language = author.config_identity.preferred_posting_language
+
             # Make the Post object
             post = cls.objects.create(
                 author=author,
@@ -502,6 +510,7 @@ def create_local(
                 visibility=visibility,
                 hashtags=hashtags,
                 in_reply_to=reply_to.object_uri if reply_to else None,
+                language=language,
             )
             post.object_uri = post.urls.object_uri
             post.url = post.absolute_object_uri()
@@ -526,6 +535,7 @@ def edit_local(
         visibility: int = Visibilities.public,
         attachments: list | None = None,
         attachment_attributes: list | None = None,
+        language: str | None = None,
     ):
         with transaction.atomic():
             # Strip all HTML and apply linebreaks filter
@@ -538,6 +548,9 @@ def edit_local(
             self.summary = summary or None
             self.sensitive = bool(summary) if sensitive is None else sensitive
             self.visibility = visibility
+            if language is None or language == "":
+                language = self.author.config_identity.preferred_posting_language
+            self.language = language
             self.edited = timezone.now()
             self.mentions.set(self.mentions_from_content(content, self.author))
             self.emojis.set(Emoji.emojis_from_content(content, None))
@@ -649,6 +662,10 @@ def to_ap(self) -> dict:
             "tag": [],
             "attachment": [],
         }
+        if self.language != "":
+            value["contentMap"] = {
+                self.language: value["content"],
+            }
         if self.type == Post.Types.question and self.type_data:
             value[self.type_data.mode] = [
                 {
@@ -872,6 +889,7 @@ def by_ap(cls, data, create=False, update=False, fetch_author=False) -> "Post":
             post.published = parse_ld_date(data.get("published"))
             post.edited = parse_ld_date(data.get("updated"))
             post.in_reply_to = data.get("inReplyTo")
+            post.language = get_language(data) or ""
             # Mentions and hashtags
             post.hashtags = []
             for tag in get_list(data, "tag"):
@@ -1106,12 +1124,16 @@ def to_mastodon_json(self, interactions=None, bookmarks=None, identity=None):
             self.Visibilities.mentioned: "direct",
             self.Visibilities.local_only: "public",
         }
+        language = self.language
+        if self.language == "":
+            language = None
         value = {
             "id": self.pk,
             "uri": self.object_uri,
             "created_at": format_ld_date(self.published),
             "account": self.author.to_mastodon_json(include_counts=False),
             "content": self.safe_content_remote(),
+            "language": language,
             "visibility": visibility_mapping[self.visibility],
             "sensitive": self.sensitive,
             "spoiler_text": self.summary or "",
@@ -1152,7 +1174,6 @@ def to_mastodon_json(self, interactions=None, bookmarks=None, identity=None):
             if isinstance(self.type_data, QuestionData)
             else None,
             "card": None,
-            "language": None,
             "text": self.safe_content_remote(),
             "edited_at": format_ld_date(self.edited) if self.edited else None,
         }
diff --git a/api/schemas.py b/api/schemas.py
index 3be6b059b..f2996b728 100644
--- a/api/schemas.py
+++ b/api/schemas.py
@@ -151,7 +151,7 @@ class Status(Schema):
     reblog: Optional["Status"] = Field(...)
     poll: Poll | None = Field(...)
     card: None = Field(...)
-    language: None = Field(...)
+    language: str | None = Field(...)
     text: str | None = Field(...)
     edited_at: str | None
     favourited: bool = False
@@ -422,13 +422,19 @@ def from_identity(
             activities_models.Post.Visibilities.mentioned: "direct",
             activities_models.Post.Visibilities.local_only: "public",
         }
+        preferred_posting_language = None
+        if identity.config_identity.preferred_posting_language != "":
+            preferred_posting_language = (
+                identity.config_identity.preferred_posting_language
+            )
+
         return cls.parse_obj(
             {
                 "posting:default:visibility": visibility_mapping[
                     identity.config_identity.default_post_visibility
                 ],
                 "posting:default:sensitive": False,
-                "posting:default:language": None,
+                "posting:default:language": preferred_posting_language,
                 "reading:expand:media": "default",
                 "reading:expand:spoilers": identity.config_identity.expand_content_warnings,
             }
diff --git a/api/views/statuses.py b/api/views/statuses.py
index 4e20993cd..e9db890ee 100644
--- a/api/views/statuses.py
+++ b/api/views/statuses.py
@@ -110,6 +110,7 @@ def post_status(request, details: PostStatusSchema) -> schemas.Status:
         reply_to=reply_post,
         attachments=attachments,
         question=details.poll.dict() if details.poll else None,
+        language=details.language,
     )
     # Add their own timeline event for immediate visibility
     TimelineEvent.add_post(request.identity, post)
@@ -141,6 +142,7 @@ def edit_status(request, id: str, details: EditStatusSchema) -> schemas.Status:
         sensitive=details.sensitive,
         attachments=attachments,
         attachment_attributes=details.media_attributes,
+        language=details.language,
     )
     return schemas.Status.from_post(post)
 
diff --git a/core/ld.py b/core/ld.py
index 8bbc08894..91294ed6e 100644
--- a/core/ld.py
+++ b/core/ld.py
@@ -1,5 +1,6 @@
 import datetime
 import os
+import re
 import urllib.parse as urllib_parse
 
 from dateutil import parser
@@ -692,3 +693,24 @@ def media_type_from_filename(filename):
         return "image/webp"
     else:
         return "application/octet-stream"
+
+
+def get_language(data) -> str | None:
+    """Detects and returns a document's language"""
+    map_ = None
+    if "contentMap" in data:
+        map_ = data["contentMap"]
+    elif "nameMap" in data:
+        map_ = data["nameMap"]
+    elif "summaryMap" in data:
+        map_ = data["summaryMap"]
+
+    if not map_:
+        return None
+
+    lang = list(map_.keys())[0]
+    if not lang or lang == "und":
+        return None
+
+    lang = re.split("-|_", lang)[0]
+    return lang.lower()
diff --git a/core/models/config.py b/core/models/config.py
index 544478b79..89f706102 100644
--- a/core/models/config.py
+++ b/core/models/config.py
@@ -286,6 +286,7 @@ class IdentityOptions(pydantic.BaseModel):
         visible_reaction_counts: bool = True
         expand_content_warnings: bool = False
         boosts_on_profile: bool = True
+        preferred_posting_language: str = ""
 
     class DomainOptions(pydantic.BaseModel):
         site_name: str = ""
diff --git a/requirements.txt b/requirements.txt
index 04b966d40..927b2b44e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -16,6 +16,7 @@ httpx~=0.23
 markdown_it_py~=2.1.0
 pillow~=9.3.0
 psycopg~=3.1.8
+pycountry~=22.3.5
 pydantic~=1.10.2
 pyld~=2.0.3
 pylibmc~=1.6.3
diff --git a/templates/activities/_post.html b/templates/activities/_post.html
index 6834ffbf4..cbdf35228 100644
--- a/templates/activities/_post.html
+++ b/templates/activities/_post.html
@@ -32,7 +32,7 @@
         </div>
     {% endif %}
 
-    <div class="content {% if post.summary %}hidden {% endif %}">
+    <div class="content {% if post.summary %}hidden {% endif %}"{% if post.language %} lang="{{ post.language }}"{% endif %}>
         {{ post.safe_content_local }}
 
         {% if post.attachments.exists %}
diff --git a/tests/activities/models/test_post.py b/tests/activities/models/test_post.py
index 3b28b14a4..4a13fee0f 100644
--- a/tests/activities/models/test_post.py
+++ b/tests/activities/models/test_post.py
@@ -259,6 +259,7 @@ def test_content_map(remote_identity):
         create=True,
     )
     assert post.content == "Hi World"
+    assert post.language == ""
 
     post2 = Post.by_ap(
         data={
@@ -271,6 +272,7 @@ def test_content_map(remote_identity):
         create=True,
     )
     assert post2.content == "Hey World"
+    assert post2.language == ""
 
     post3 = Post.by_ap(
         data={
@@ -283,6 +285,7 @@ def test_content_map(remote_identity):
         create=True,
     )
     assert post3.content == "Hello World"
+    assert post3.language == "en"
 
 
 @pytest.mark.django_db
diff --git a/tests/core/test_ld.py b/tests/core/test_ld.py
index 4f123173b..fb409a773 100644
--- a/tests/core/test_ld.py
+++ b/tests/core/test_ld.py
@@ -2,7 +2,7 @@
 
 from dateutil.tz import tzutc
 
-from core.ld import parse_ld_date
+from core.ld import get_language, parse_ld_date
 
 
 def test_parse_ld_date():
@@ -41,3 +41,41 @@ def test_parse_ld_date():
         tzinfo=tzutc(),
     )
     assert difference.total_seconds() == 0
+
+
+def test_get_language():
+    assert (
+        get_language(
+            {
+                "contentMap": {
+                    "en": "<p>Hello</p>",
+                    "es": "<p>hola</p>",
+                },
+                "nameMap": {"de": "Hallo"},
+                "summaryMap": {"fr": "Bonjour"},
+            }
+        )
+        == "en"
+    )
+    assert (
+        get_language(
+            {
+                "nameMap": {"de": "Hallo"},
+                "summaryMap": {"fr": "Bonjour"},
+            }
+        )
+        == "de"
+    )
+    assert (
+        get_language(
+            {
+                "summaryMap": {"fr": "Bonjour"},
+            }
+        )
+        == "fr"
+    )
+    assert get_language({"contentMap": {"en-gb": "<p>Hello</p>"}}) == "en"
+    assert get_language({"contentMap": {"en_GB": "<p>Hello</p>"}}) == "en"
+    assert get_language({"contentMap": {"EN": "<p>Hello</p>"}}) == "en"
+    assert get_language({"contentMap": {"und": "<p>Hello</p>"}}) is None
+    assert get_language({}) is None
diff --git a/users/views/settings/posting.py b/users/views/settings/posting.py
index 3916f1e6b..de393577b 100644
--- a/users/views/settings/posting.py
+++ b/users/views/settings/posting.py
@@ -1,3 +1,5 @@
+import pycountry
+
 from activities.models.post import Post
 from users.views.settings.settings_page import SettingsPage
 
@@ -15,8 +17,29 @@ class PostingPage(SettingsPage):
             "title": "Expand content warnings",
             "help_text": "If content warnings should be expanded by default (not honoured by all clients)",
         },
+        "preferred_posting_language": {
+            "title": "Default posting language",
+            "help_text": "",
+            "choices": sorted(
+                (
+                    [
+                        ("", ""),
+                    ]
+                    + [
+                        (lang.alpha_2, lang.name)
+                        for lang in pycountry.languages
+                        if hasattr(lang, "alpha_2")
+                    ]
+                ),
+                key=lambda lang: lang[1],
+            ),
+        },
     }
 
     layout = {
-        "Posting": ["default_post_visibility", "expand_content_warnings"],
+        "Posting": [
+            "default_post_visibility",
+            "expand_content_warnings",
+            "preferred_posting_language",
+        ],
     }
diff --git a/users/views/settings/settings_page.py b/users/views/settings/settings_page.py
index ab5d4b2f1..5b305cbd0 100644
--- a/users/views/settings/settings_page.py
+++ b/users/views/settings/settings_page.py
@@ -23,7 +23,7 @@ class SettingsPage(FormView):
     options_class = Config.IdentityOptions
     template_name = "settings/settings.html"
     section: ClassVar[str]
-    options: dict[str, dict[str, str | int]]
+    options: dict[str, dict[str, str | int | list[tuple[int | str, str]]]]
     layout: dict[str, list[str]]
 
     def get_form_class(self):
@@ -42,7 +42,11 @@ def get_form_class(self):
             elif config_field.type_ is UploadedImage:
                 form_field = forms.ImageField
             elif config_field.type_ is str:
-                if details.get("display") == "textarea":
+                choices = details.get("choices")
+                if choices:
+                    field_kwargs["widget"] = forms.Select(choices=choices)
+                    form_field = forms.CharField
+                elif details.get("display") == "textarea":
                     form_field = partial(
                         forms.CharField,
                         widget=forms.Textarea,