diff --git a/src/modules/processing/match.js b/src/modules/processing/match.js
index e06166db..eb2d64a9 100644
--- a/src/modules/processing/match.js
+++ b/src/modules/processing/match.js
@@ -18,6 +18,7 @@ import soundcloud from "./services/soundcloud.js";
 import instagram from "./services/instagram.js";
 import vine from "./services/vine.js";
 import pinterest from "./services/pinterest.js";
+import nicovideo from "./services/nicovideo.js";
 
 export default async function (host, patternMatch, url, lang, obj) {
     try {
@@ -114,6 +115,9 @@ export default async function (host, patternMatch, url, lang, obj) {
             case "pinterest":
                 r = await pinterest({ id: patternMatch["id"] });
                 break;
+            case "nicovideo":
+                r = await nicovideo({ id: patternMatch["id"] });
+                break;
             default:
                 return apiJSON(0, { t: errorUnsupported(lang) });
         }
diff --git a/src/modules/processing/services/nicovideo.js b/src/modules/processing/services/nicovideo.js
new file mode 100644
index 00000000..eb76a123
--- /dev/null
+++ b/src/modules/processing/services/nicovideo.js
@@ -0,0 +1,130 @@
+import { genericUserAgent, maxVideoDuration } from "../../config.js";
+
+/**
+ * Regex for parsing the HTML element containing the JSON object used to
+ * authenticate the request for the video stream.
+ */
+const JS_INITIAL_WATCH_DATA_REGEX = /<div[^>]+id="js-initial-watch-data"[^>]+data-api-data="([^"]+)"/;
+
+/**
+ * Undo html escaping. e.g. `&quot;` -> `"`
+ *
+ * @param {string} input Possibly escaped string
+ *
+ * @returns `input` with escaped characters un-escaped
+ */
+const unescapeHtml = input => {
+    return input
+        .replaceAll("&amp;", "&")
+        .replaceAll("&lt;", "<")
+        .replaceAll("&gt;", ">")
+        .replaceAll("&quot;", "\"")
+        .replaceAll("&#039;", "'");
+}
+
+export default async function(obj) {
+    // Step 1: We need to retrieve a JSON object from an element with ID
+    // `js-initial-watch-data`.
+    const videoPageBody = await fetch(`https://www.nicovideo.jp/watch/${obj.id}`, {
+        headers: { "user-agent": genericUserAgent }
+    }).then(res => res.text());
+
+    const matches = JS_INITIAL_WATCH_DATA_REGEX.exec(videoPageBody);
+    if (matches?.length < 2) return { error: 'ErrorCouldntFetch' }; 
+
+    const jsonStr = unescapeHtml(matches[1]);
+
+    let jsInitialWatchData = null;
+    try {
+        jsInitialWatchData = JSON.parse(jsonStr);
+    } catch (_err) {
+        return { error: 'ErrorCouldntFetch' };
+    }
+
+    const { video } = jsInitialWatchData;
+    if (!video || !video.duration) {
+        return { error: 'ErrorCouldntFetch' };
+    }
+    if (video.duration > maxVideoDuration * 1000) {
+        return { error: ['ErrorLengthLimit', maxVideoDuration / 60000] };
+    }
+
+    // Step 2: We use the JSON object to send an HTTP request to retrieve
+    // the m3u8 for the video stream.
+    const { session } = jsInitialWatchData?.media?.delivery?.movie;
+    if (!session) {
+        return { error: 'ErrorCouldntFetch' };
+    }
+    const body = {
+        session: {
+            client_info: {
+                player_id: session.playerId,
+            },
+            content_auth: {
+                auth_type: session.authTypes.http,
+                content_key_timeout: 600000,
+                service_id: "nicovideo",
+                service_user_id: session.serviceUserId
+            },
+            content_id: session.contentId,
+            content_src_id_sets: [{
+                content_src_ids: [{
+                    src_id_to_mux: {
+                        video_src_ids: session.videos,
+                        audio_src_ids: session.audios
+                    }
+                }]
+            }],
+            content_type: "movie",
+            content_uri: "",
+            keep_method: {
+                heartbeat: {
+                    lifetime: 120000
+                }
+            },
+            priority: 0,
+            protocol: {
+                name: "http",
+                parameters: {
+                    http_parameters: {
+                        parameters: {
+                            hls_parameters: {
+                                use_well_known_port: "yes",
+                                use_ssl: "yes",
+                                transfer_preset: "",
+                                segment_duration: 6000
+                            }
+                        }
+                    }
+                }
+            },
+            recipe_id: session.recipeId,
+            session_operation_auth: {
+                session_operation_auth_by_signature: {
+                    signature: session.signature,
+                    token: session.token
+                }
+            },
+            timing_constraint: "unlimited"
+        }
+    };
+    const res = await fetch("https://api.dmc.nico/api/sessions?_format=json", {
+        method: "POST",
+        body: JSON.stringify(body)
+    }).then(res => res.json());
+
+    if (res?.meta?.status !== 201) {
+        return { error: 'ErrorCouldntFetch' };
+    }
+
+    const playlistUri = res?.data?.session?.content_uri;
+    if (!playlistUri) {
+        return { error: 'ErrorCouldntFetch' };
+    }
+
+    return {
+        urls: playlistUri,
+        isM3U8: true,
+        filename: `nicovideo_${obj.id}.mp4`
+    } 
+}
diff --git a/src/modules/processing/servicesConfig.json b/src/modules/processing/servicesConfig.json
index 1890edac..6ec8d637 100644
--- a/src/modules/processing/servicesConfig.json
+++ b/src/modules/processing/servicesConfig.json
@@ -67,6 +67,12 @@
             "alias": "pinterest videos & stories",
             "patterns": ["pin/:id"],
             "enabled": true
+        },
+        "nicovideo": {
+            "alias": "niconico videos",
+            "patterns": ["watch/:id"],
+            "enabled": true,
+            "tld": "jp"
         }
     }    
 }
diff --git a/src/modules/processing/servicesPatternTesters.js b/src/modules/processing/servicesPatternTesters.js
index e3286c37..0d12a221 100644
--- a/src/modules/processing/servicesPatternTesters.js
+++ b/src/modules/processing/servicesPatternTesters.js
@@ -30,5 +30,6 @@ export const testers = {
     
     "vine": (patternMatch) => (patternMatch["id"] && patternMatch["id"].length <= 12),
     
-    "pinterest": (patternMatch) => (patternMatch["id"] && patternMatch["id"].length <= 128)
+    "pinterest": (patternMatch) => (patternMatch["id"] && patternMatch["id"].length <= 128),
+    "nicovideo": (patternMatch) => (patternMatch["id"] && patternMatch["id"].startsWith("sm") && patternMatch["id"].length === 10)
 }
diff --git a/src/modules/stream/types.js b/src/modules/stream/types.js
index 6fee9a43..311ba91f 100644
--- a/src/modules/stream/types.js
+++ b/src/modules/stream/types.js
@@ -148,7 +148,15 @@ export function streamVideoOnly(streamInfo, res) {
         ]
         if (streamInfo.mute) args.push('-an');
         if (streamInfo.service === "vimeo") args.push('-bsf:a', 'aac_adtstoasc');
-        if (format === "mp4") args.push('-movflags', 'faststart+frag_keyframe+empty_moov');
+        if (format === "mp4") {
+            // for some reason, downloading nicovideo with the `empty_moov` flag
+            // will only download one second of video
+            // TODO: figure out why
+            const movflags = streamInfo.service === 'nicovideo'
+                ? 'faststart+frag_keyframe'
+                : 'faststart+frag_keyframe+empty_moov';
+            args.push('-movflags', movflags);
+        }
         args.push('-f', format, 'pipe:3');
         const ffmpegProcess = spawn(ffmpeg, args, {
             windowsHide: true,