diff --git a/Dockerfile b/Dockerfile
index bf635012fd53..69fec064a788 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -234,6 +234,8 @@ COPY --from=static /opt/warehouse/src/warehouse/admin/static/dist/ /opt/warehous
 COPY --from=build /opt/warehouse/ /opt/warehouse/
 COPY . /opt/warehouse/src/
 
+# Pre-cache TLD list
+RUN tldextract --update
 # Load our module to pre-compile as much bytecode as we can easily.
 # Saves time collectively on container boot!
 RUN python -m warehouse
diff --git a/requirements/main.in b/requirements/main.in
index 068b7ff21a4c..b8d563c00c36 100644
--- a/requirements/main.in
+++ b/requirements/main.in
@@ -68,6 +68,7 @@ sqlalchemy[asyncio]>=2.0,<3.0
 stdlib-list
 stripe
 structlog
+tldextract
 transaction
 trove-classifiers
 ua-parser
diff --git a/requirements/main.txt b/requirements/main.txt
index a0c0ea9a531f..240749081224 100644
--- a/requirements/main.txt
+++ b/requirements/main.txt
@@ -514,6 +514,10 @@ email-validator==2.2.0 \
 events==0.5 \
     --hash=sha256:a7286af378ba3e46640ac9825156c93bdba7502174dd696090fdfcd4d80a1abd
     # via opensearch-py
+filelock==3.15.4 \
+    --hash=sha256:2207938cbc1844345cb01a5a95524dae30f0ce089eba5b00378295a17e3e90cb \
+    --hash=sha256:6ca1fffae96225dab4c6eaf1c4f4f28cd2568d3ec2a44e15a08520504de468e7
+    # via tldextract
 first==2.0.2 \
     --hash=sha256:8d8e46e115ea8ac652c76123c0865e3ff18372aef6f03c22809ceefcea9dec86 \
     --hash=sha256:ff285b08c55f8c97ce4ea7012743af2495c9f1291785f163722bd36f6af6d3bf
@@ -901,6 +905,7 @@ idna==3.8 \
     # via
     #   email-validator
     #   requests
+    #   tldextract
 importlib-resources==6.4.4 \
     --hash=sha256:20600c8b7361938dc0bb2d5ec0297802e575df486f5a544fa414da65e13721f7 \
     --hash=sha256:dda242603d1c9cd836c3368b1174ed74cb4049ecd209e7a1a0104620c18c5c11
@@ -1934,13 +1939,19 @@ requests==2.32.3 \
     #   opensearch-py
     #   premailer
     #   requests-aws4auth
+    #   requests-file
     #   sigstore
     #   stripe
+    #   tldextract
     #   tuf
 requests-aws4auth==1.3.1 \
     --hash=sha256:2969b5379ae6e60ee666638caf6cb94a32d67033f6bfcf0d50c95cd5474f2419 \
     --hash=sha256:b6ad4882310e03ba2538ebf94d1f001ca9feabc5c52618539cf1eb6d5af76791
     # via -r requirements/main.in
+requests-file==2.1.0 \
+    --hash=sha256:0f549a3f3b0699415ac04d167e9cb39bccfb730cb832b4d20be3d9867356e658 \
+    --hash=sha256:cf270de5a4c5874e84599fc5778303d496c10ae5e870bfa378818f35d21bda5c
+    # via tldextract
 rfc3339-validator==0.1.4 \
     --hash=sha256:138a2abdf93304ad60530167e51d2dfb9549521a836871b88d7f4695d0022f6b \
     --hash=sha256:24f6ec1eda14ef823da9e36ec7113124b39c04d50a4d3d3a3c2859577e7791fa
@@ -2181,6 +2192,10 @@ text-unidecode==1.3 \
     --hash=sha256:1311f10e8b895935241623731c2ba64f4c455287888b18189350b67134a822e8 \
     --hash=sha256:bad6603bb14d279193107714b288be206cac565dfa49aa5b105294dd5c4aab93
     # via python-slugify
+tldextract==5.1.2 \
+    --hash=sha256:4dfc4c277b6b97fa053899fcdb892d2dc27295851ab5fac4e07797b6a21b2e46 \
+    --hash=sha256:c9e17f756f05afb5abac04fe8f766e7e70f9fe387adb1859f0f52408ee060200
+    # via -r requirements/main.in
 transaction==4.0 \
     --hash=sha256:68035db913f60d1be12f6563d201daab36c83e763de15899ff8338f26e5e62f2 \
     --hash=sha256:e2519a316a05b14b3d483ac777df311087daaffeeafd3e9f7de62fc087ce3209
diff --git a/tests/unit/accounts/test_forms.py b/tests/unit/accounts/test_forms.py
index 2e888e9a0627..b6c68f440337 100644
--- a/tests/unit/accounts/test_forms.py
+++ b/tests/unit/accounts/test_forms.py
@@ -562,16 +562,17 @@ def test_disposable_email_error(self, pyramid_request):
         )
 
     @pytest.mark.parametrize(
-        "email",
+        ("email", "prohibited_domain"),
         [
-            "foo@wutang.net",
-            "foo@clan.wutang.net",
-            "foo@one.two.wutang.net",
-            "foo@wUtAnG.net",
+            ("foo@wutang.net", "wutang.net"),
+            ("foo@clan.wutang.net", "wutang.net"),
+            ("foo@one.two.wutang.net", "wutang.net"),
+            ("foo@wUtAnG.net", "wutang.net"),
+            ("foo@one.wutang.co.uk", "wutang.co.uk"),
         ],
     )
-    def test_prohibited_email_error(self, db_request, email):
-        domain = ProhibitedEmailDomain(domain="wutang.net")
+    def test_prohibited_email_error(self, db_request, email, prohibited_domain):
+        domain = ProhibitedEmailDomain(domain=prohibited_domain)
         db_request.db.add(domain)
 
         form = forms.RegistrationForm(
diff --git a/warehouse/accounts/forms.py b/warehouse/accounts/forms.py
index e27af8cb11dc..bf97dd050dcc 100644
--- a/warehouse/accounts/forms.py
+++ b/warehouse/accounts/forms.py
@@ -23,6 +23,7 @@
 import wtforms.fields
 
 from sqlalchemy import exists
+from tldextract import TLDExtract
 
 import warehouse.utils.otp as otp
 import warehouse.utils.webauthn as webauthn
@@ -285,7 +286,8 @@ def validate_email(self, field):
             )
 
         # Check if the domain is valid
-        domain = ".".join(address.domain.split(".")[-2:]).lower()
+        extractor = TLDExtract(suffix_list_urls=())  # Updated during image build
+        domain = extractor(address.domain.lower()).registered_domain
 
         if (
             domain in disposable_email_domains.blocklist
diff --git a/warehouse/locale/messages.pot b/warehouse/locale/messages.pot
index b0e6ca8bccc9..0b3cfdeef026 100644
--- a/warehouse/locale/messages.pot
+++ b/warehouse/locale/messages.pot
@@ -14,103 +14,103 @@ msgstr ""
 msgid "Locale updated"
 msgstr ""
 
-#: warehouse/accounts/forms.py:51
+#: warehouse/accounts/forms.py:52
 msgid "The password is invalid. Try again."
 msgstr ""
 
-#: warehouse/accounts/forms.py:52
+#: warehouse/accounts/forms.py:53
 msgid ""
 "The username is invalid. Usernames must be composed of letters, numbers, "
 "dots, hyphens and underscores. And must also start and finish with a "
 "letter or number. Choose a different username."
 msgstr ""
 
-#: warehouse/accounts/forms.py:70
+#: warehouse/accounts/forms.py:71
 msgid "Null bytes are not allowed."
 msgstr ""
 
-#: warehouse/accounts/forms.py:93
+#: warehouse/accounts/forms.py:94
 msgid "No user found with that username"
 msgstr ""
 
-#: warehouse/accounts/forms.py:104
+#: warehouse/accounts/forms.py:105
 msgid "TOTP code must be ${totp_length} digits."
 msgstr ""
 
-#: warehouse/accounts/forms.py:124
+#: warehouse/accounts/forms.py:125
 msgid "Recovery Codes must be ${recovery_code_length} characters."
 msgstr ""
 
-#: warehouse/accounts/forms.py:139
+#: warehouse/accounts/forms.py:140
 msgid "Choose a username with 50 characters or less."
 msgstr ""
 
-#: warehouse/accounts/forms.py:156
+#: warehouse/accounts/forms.py:157
 msgid ""
 "This username is already being used by another account. Choose a "
 "different username."
 msgstr ""
 
-#: warehouse/accounts/forms.py:170 warehouse/accounts/forms.py:219
-#: warehouse/accounts/forms.py:232
+#: warehouse/accounts/forms.py:171 warehouse/accounts/forms.py:220
+#: warehouse/accounts/forms.py:233
 msgid "Password too long."
 msgstr ""
 
-#: warehouse/accounts/forms.py:206
+#: warehouse/accounts/forms.py:207
 msgid ""
 "There have been too many unsuccessful login attempts. You have been "
 "locked out for ${time}. Please try again later."
 msgstr ""
 
-#: warehouse/accounts/forms.py:235
+#: warehouse/accounts/forms.py:236
 msgid "Your passwords don't match. Try again."
 msgstr ""
 
-#: warehouse/accounts/forms.py:269
+#: warehouse/accounts/forms.py:270
 msgid "The email address is too long. Try again."
 msgstr ""
 
-#: warehouse/accounts/forms.py:284
+#: warehouse/accounts/forms.py:285
 msgid "The email address isn't valid. Try again."
 msgstr ""
 
-#: warehouse/accounts/forms.py:297
+#: warehouse/accounts/forms.py:299
 msgid "You can't use an email address from this domain. Use a different email."
 msgstr ""
 
-#: warehouse/accounts/forms.py:308
+#: warehouse/accounts/forms.py:310
 msgid ""
 "This email address is already being used by this account. Use a different"
 " email."
 msgstr ""
 
-#: warehouse/accounts/forms.py:315
+#: warehouse/accounts/forms.py:317
 msgid ""
 "This email address is already being used by another account. Use a "
 "different email."
 msgstr ""
 
-#: warehouse/accounts/forms.py:348 warehouse/manage/forms.py:139
+#: warehouse/accounts/forms.py:350 warehouse/manage/forms.py:139
 msgid "The name is too long. Choose a name with 100 characters or less."
 msgstr ""
 
-#: warehouse/accounts/forms.py:440
+#: warehouse/accounts/forms.py:442
 msgid "Invalid TOTP code."
 msgstr ""
 
-#: warehouse/accounts/forms.py:457
+#: warehouse/accounts/forms.py:459
 msgid "Invalid WebAuthn assertion: Bad payload"
 msgstr ""
 
-#: warehouse/accounts/forms.py:526
+#: warehouse/accounts/forms.py:528
 msgid "Invalid recovery code."
 msgstr ""
 
-#: warehouse/accounts/forms.py:535
+#: warehouse/accounts/forms.py:537
 msgid "Recovery code has been previously used."
 msgstr ""
 
-#: warehouse/accounts/forms.py:565
+#: warehouse/accounts/forms.py:567
 msgid "The username isn't valid. Try again."
 msgstr ""