diff --git a/docs/supportedsites.md b/docs/supportedsites.md
index 947442f9..eed7aa10 100644
--- a/docs/supportedsites.md
+++ b/docs/supportedsites.md
@@ -631,6 +631,12 @@ Consider all sites to be NSFW unless otherwise known.
     <td>Articles, Tag Searches</td>
     <td></td>
 </tr>
+<tr>
+    <td>Seiso</td>
+    <td>https://seiso.party/</td>
+    <td>Posts, User Profiles</td>
+    <td></td>
+</tr>
 <tr>
     <td>Sen Manga</td>
     <td>https://raw.senmanga.com/</td>
diff --git a/gallery_dl/extractor/__init__.py b/gallery_dl/extractor/__init__.py
index d927d708..d07c0636 100644
--- a/gallery_dl/extractor/__init__.py
+++ b/gallery_dl/extractor/__init__.py
@@ -105,6 +105,7 @@ modules = [
     "sankaku",
     "sankakucomplex",
     "seiga",
+    "seisoparty",
     "senmanga",
     "sexcom",
     "simplyhentai",
diff --git a/gallery_dl/extractor/seisoparty.py b/gallery_dl/extractor/seisoparty.py
new file mode 100644
index 00000000..3dc89dee
--- /dev/null
+++ b/gallery_dl/extractor/seisoparty.py
@@ -0,0 +1,131 @@
+# -*- coding: utf-8 -*-
+
+# Copyright 2021 Mike Fährmann
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+
+"""Extractors for https://seiso.party/"""
+
+from .common import Extractor, Message
+from .. import text
+import re
+
+
+class SeisopartyExtractor(Extractor):
+    """Base class for seisoparty extractors"""
+    category = "seisoparty"
+    root = "https://seiso.party"
+    directory_fmt = ("{category}", "{service}", "{user}")
+    filename_fmt = "{id}_{title}_{num:>02}_{filename}.{extension}"
+    archive_fmt = "{service}_{user}_{id}_{num}"
+
+    def __init__(self, match):
+        Extractor.__init__(self, match)
+        self.user_name = None
+        self._find_files = re.compile(
+            r'href="(https://cdn\.seiso\.party/files/[^"]+)').findall
+
+    def items(self):
+        for post in self.posts():
+            files = post.pop("files")
+            yield Message.Directory, post
+            for post["num"], url in enumerate(files, 1):
+                yield Message.Url, url, text.nameext_from_url(url, post)
+
+    def _parse_post(self, page, post_id):
+        extr = text.extract_from(page)
+        return {
+            "service" : self.service,
+            "user"    : self.user_id,
+            "username": self.user_name,
+            "id"      : post_id,
+            "date"    : text.parse_datetime(extr(
+                '<div class="margin-bottom-15 minor-text">', '<'),
+                "%Y-%m-%d %H:%M:%S %Z"),
+            "title"   : text.unescape(extr('class="post-title">', '<')),
+            "content" : text.unescape(extr("\n<p>\n", "\n</p>\n").strip()),
+            "files"   : self._find_files(page),
+        }
+
+
+class SeisopartyUserExtractor(SeisopartyExtractor):
+    """Extractor for all posts from a seiso.party user listing"""
+    subcategory = "user"
+    pattern = r"(?:https?://)?seiso\.party/artists/([^/?#]+)/([^/?#]+)"
+    test = (
+        ("https://seiso.party/artists/fanbox/21", {
+            "pattern": r"https://cdn\.seiso\.party/files/fanbox/\d+/",
+            "count": ">=15",
+            "keyword": {
+                "content": str,
+                "date": "type:datetime",
+                "id": r"re:\d+",
+                "num": int,
+                "service": "fanbox",
+                "title": str,
+                "user": "21",
+                "username": "雨",
+            },
+        }),
+    )
+
+    def __init__(self, match):
+        SeisopartyExtractor.__init__(self, match)
+        self.service, self.user_id = match.groups()
+
+    def posts(self):
+        url = "{}/artists/{}/{}".format(self.root, self.service, self.user_id)
+        page = self.request(url).text
+        self.user_name, pos = text.extract(page, '<span class="title">', '<')
+
+        url = self.root + text.extract(
+            page, 'href="', '"', page.index('id="content"', pos))[0]
+        response = self.request(url)
+        headers = {"Referer": url}
+
+        while True:
+            yield self._parse_post(response.text, url.rpartition("/")[2])
+            response = self.request(url + "/next", headers=headers)
+            if url == response.url:
+                return
+            url = headers["Referer"] = response.url
+
+
+class SeisopartyPostExtractor(SeisopartyExtractor):
+    """Extractor for a single seiso.party post"""
+    subcategory = "post"
+    pattern = r"(?:https?://)?seiso\.party/post/([^/?#]+)/([^/?#]+)/([^/?#]+)"
+    test = (
+        ("https://seiso.party/post/fanbox/21/371", {
+            "url": "75f13b92de0ce399b6163c3de18f1f36011c2366",
+            "count": 2,
+            "keyword": {
+                "content": "この前描いためぐるちゃんのPSDファイルです。\n"
+                           "どうぞよろしくお願いします。",
+                "date": "dt:2021-05-06 12:38:31",
+                "extension": "re:psd|jpg",
+                "filename": "re:backcourt|ffb2ccb7a3586d05f9a4620329dd131e",
+                "id": "371",
+                "num": int,
+                "service": "fanbox",
+                "title": "MEGURU.PSD",
+                "user": "21",
+                "username": "雨",
+            },
+        }),
+    )
+
+    def __init__(self, match):
+        SeisopartyExtractor.__init__(self, match)
+        self.service, self.user_id, self.post_id = match.groups()
+
+    def posts(self):
+        url = "{}/artists/{}/{}".format(self.root, self.service, self.user_id)
+        page = self.request(url).text
+        self.user_name, pos = text.extract(page, '<span class="title">', '<')
+
+        url = "{}/post/{}/{}/{}".format(
+            self.root, self.service, self.user_id, self.post_id)
+        return (self._parse_post(self.request(url).text, self.post_id),)
diff --git a/scripts/supportedsites.py b/scripts/supportedsites.py
index 0e81f2dd..1bb5d654 100755
--- a/scripts/supportedsites.py
+++ b/scripts/supportedsites.py
@@ -90,6 +90,7 @@ CATEGORY_MAP = {
     "sankakucomplex" : "Sankaku Complex",
     "seaotterscans"  : "Sea Otter Scans",
     "seiga"          : "Niconico Seiga",
+    "seisoparty"     : "Seiso",
     "senmanga"       : "Sen Manga",
     "sensescans"     : "Sense-Scans",
     "sexcom"         : "Sex.com",
diff --git a/test/test_results.py b/test/test_results.py
index 9c6845d2..43b2f739 100644
--- a/test/test_results.py
+++ b/test/test_results.py
@@ -317,6 +317,8 @@ def setup_test_config():
 
     config.set(("extractor", "kemonoparty"), "cookies", {
         "__ddg1": "0gBDGpJ3KZQmA4B9QH25", "__ddg2": "lmj5s1jnJOvhPXCX"})
+    config.set(("extractor", "seisoparty"), "cookies", {
+        "__ddg1": "Y8rBxSDHO5UCEtQvzyI9", "__ddg2": "lmj5s1jnJOvhPXCX"})
 
     config.set(("extractor", "mastodon.social"), "access-token",
                "Blf9gVqG7GytDTfVMiyYQjwVMQaNACgf3Ds3IxxVDUQ")