diff --git a/yt_dlp/extractor/_extractors.py b/yt_dlp/extractor/_extractors.py
index a3610dc976..7f96b08e65 100644
--- a/yt_dlp/extractor/_extractors.py
+++ b/yt_dlp/extractor/_extractors.py
@@ -2243,6 +2243,10 @@
 from .ukcolumn import UkColumnIE
 from .uktvplay import UKTVPlayIE
 from .umg import UMGDeIE
+from .underline import (
+    UnderlinePosterIE,
+    UnderlinePosterListIE,
+)
 from .unistra import UnistraIE
 from .unity import UnityIE
 from .unsupported import (
diff --git a/yt_dlp/extractor/underline.py b/yt_dlp/extractor/underline.py
new file mode 100644
index 0000000000..f89834d303
--- /dev/null
+++ b/yt_dlp/extractor/underline.py
@@ -0,0 +1,123 @@
+import functools
+
+from .common import InfoExtractor
+from ..utils import (
+    OnDemandPagedList,
+    filter_dict,
+    update_url,
+    url_or_none,
+)
+from ..utils.traversal import traverse_obj
+
+
+class UnderlinePosterIE(InfoExtractor):
+    _VALID_URL = r'https://(?:www\.)?underline\.io/events/\d+/posters/\d+/poster/(?P<id>\d+)-[\w-]+/?(?:[#?]|$)'
+
+    _TESTS = [{
+        # Video and PPT
+        'url': 'https://underline.io/events/342/posters/12863/poster/66466-towards-a-general-purpose-machine-translation-system-for-sranantongo',
+        'info_dict': {
+            'id': '66466',
+            'ext': 'mp4',
+            'title': 'Towards a general purpose machine translation system for Sranantongo',
+            'thumbnail': 'https://assets.underline.io/lecture/66466/poster_document_thumbnail_extract/2a8d3abd5a5edbf0117d8d9bdf018e6d.jpg',
+            'live_status': 'not_live',
+        },
+    }, {
+        # PPT only
+        'url': 'https://underline.io/events/342/posters/12863/poster/66459-low-resourced-multilingual-neural-machine-translation-for-ometo-english',
+        'info_dict': {
+            'id': '66459',
+            'title': 'Low Resourced Multilingual Neural Machine Translation for Ometo-English',
+            'thumbnail': 'https://assets.underline.io/lecture/66459/poster_document_thumbnail_extract/69a3fd48e3bb137ddcf3099db637d184.jpg',
+            'live_status': 'not_live',
+        },
+        'params': {
+            'skip_download': True,
+            'ignore_no_formats_error': True,
+        },
+        'expected_warnings': ['No video formats found!', 'Requested format is not available'],
+    }, {
+        'url': 'https://www.underline.io/events/342/posters/12863/poster/66463-mbti-personality-prediction-approach-on-persian-twitter/?tab=video',
+        'only_matching': True,
+    }]
+
+    def _real_extract(self, url):
+        video_id = self._match_id(url)
+        webpage = self._download_webpage(url, video_id)
+
+        data = self._search_nextjs_data(webpage, video_id)['props']['pageProps']['fallback']
+
+        m3u8_url = traverse_obj(data, (..., 'data', 'attributes', 'playlist', {url_or_none}), get_all=False)
+        subtitle_urls = filter_dict(dict(traverse_obj(data, (..., 'data', lambda _, v: v['type'] == 'transcripts', {
+            lambda x: (
+                x['relationships']['language']['data']['id'],
+                url_or_none(x['attributes']['subtitleUrl']),
+            )}))))
+
+        return {
+            'id': video_id,
+            'title': traverse_obj(data, (..., 'data', 'attributes', 'title', {str}), get_all=False),
+            'thumbnail': traverse_obj(
+                data, (..., 'data', 'attributes', 'originalPosterDocumentThumbnailExtractUrl', {url_or_none}), get_all=False),
+            'formats': self._extract_m3u8_formats(m3u8_url, video_id, fatal=False) if m3u8_url else [],
+            'subtitles': filter_dict(dict(traverse_obj(data, (
+                ..., 'included', lambda _, v: v['type'] == 'transcript_languages', {lambda x: (
+                    x['attributes']['locale'],
+                    [{'url': subtitle_urls[x['id']]}],
+                )})))),
+            'live_status': 'not_live',
+        }
+
+
+class UnderlinePosterListIE(InfoExtractor):
+    _VALID_URL = r'https://(?:www\.)?underline\.io/events/(?P<event_id>\d+)/posters/?\?(?:[^&]+&)*?eventSessionId=(?P<event_session_id>\d+)(?:&|#)?'
+    _HEADERS = {'Accept': 'application/vnd.api+json'}
+    _PAGE_SIZE = 16
+
+    _TESTS = [{
+        'url': 'https://underline.io/events/342/posters?eventSessionId=12863',
+        'info_dict': {
+            'id': '12863',
+            'title': 'W13 (WiNLP) The Sixth Widening NLP Workshop',
+            'description': r're:.+Isidora Tourni and Surangika Ranathunga.+',
+        },
+        'playlist_mincount': 10,
+    }, {
+        'url': 'https://www.underline.io/events/342/posters?searchGroup=lecture&eventSessionId=12860',
+        'only_matching': True,
+    }]
+
+    def _fetch_paged_channel_video_list(self, list_url, event_id, event_session_id, page):
+        page_num = page + 1
+        video_url_tmpl = f'https://underline.io/events/{event_id}/posters/{event_session_id}/poster/{{id}}-{{slug}}'
+
+        page_info = self._download_json(update_url(
+            list_url, query_update={'page[number]': page_num}), event_session_id, headers=self._HEADERS,
+            note=f'Downloading list info (page {page_num})', errnote=f'Failed to download list info (page {page_num})')
+
+        yield from traverse_obj(page_info, (
+            'data', ..., {lambda x: video_url_tmpl.format(id=x['id'], slug=x['attributes']['slug'])}, {self.url_result}))
+
+    def _real_extract(self, url):
+        event_id, event_session_id = self._match_valid_url(url).groups()
+
+        event_info = self._download_json(
+            f'https://app.underline.io/api/v1/thin_event_sessions/{event_session_id}', event_session_id, headers=self._HEADERS,
+            note='Downloading event session info', errnote='Failed to download event session info')
+
+        return self.playlist_result(OnDemandPagedList(functools.partial(
+            self._fetch_paged_channel_video_list,
+            update_url('https://app.underline.io/api/v1/thin_lectures', query_update={
+                'filter[poster_lecture]': 'true',
+                'filter[published]': 'all',
+                'sort': 'held_at,id',
+                'include': 'sorted_profiles,event_session,tag,event',
+                'filter[scope]': 'all',
+                'filter[event_id]': event_id,
+                'filter[event_session_id]': event_session_id,
+                'page[size]': self._PAGE_SIZE,
+            }), event_id, event_session_id), self._PAGE_SIZE),
+            event_session_id,
+            traverse_obj(event_info, ('data', 'attributes', 'name'), get_all=False),
+            traverse_obj(event_info, ('data', 'attributes', 'description'), get_all=False))