diff --git a/src/ja/ganganonline/build.gradle b/src/ja/ganganonline/build.gradle
new file mode 100644
index 000000000..599be39b1
--- /dev/null
+++ b/src/ja/ganganonline/build.gradle
@@ -0,0 +1,7 @@
+ext {
+    extName = 'Gangan Online'
+    extClass = '.GanganOnline'
+    extVersionCode = 1
+    isNsfw = false
+}
+apply from: "$rootDir/common.gradle"
diff --git a/src/ja/ganganonline/res/mipmap-hdpi/ic_launcher.png b/src/ja/ganganonline/res/mipmap-hdpi/ic_launcher.png
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diff --git a/src/ja/ganganonline/res/mipmap-mdpi/ic_launcher.png b/src/ja/ganganonline/res/mipmap-mdpi/ic_launcher.png
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index 000000000..f609ae3d2
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diff --git a/src/ja/ganganonline/res/mipmap-xhdpi/ic_launcher.png b/src/ja/ganganonline/res/mipmap-xhdpi/ic_launcher.png
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diff --git a/src/ja/ganganonline/res/mipmap-xxhdpi/ic_launcher.png b/src/ja/ganganonline/res/mipmap-xxhdpi/ic_launcher.png
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diff --git a/src/ja/ganganonline/res/mipmap-xxxhdpi/ic_launcher.png b/src/ja/ganganonline/res/mipmap-xxxhdpi/ic_launcher.png
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diff --git a/src/ja/ganganonline/src/eu/kanade/tachiyomi/extension/ja/ganganonline/Dto.kt b/src/ja/ganganonline/src/eu/kanade/tachiyomi/extension/ja/ganganonline/Dto.kt
new file mode 100644
index 000000000..59c65711b
--- /dev/null
+++ b/src/ja/ganganonline/src/eu/kanade/tachiyomi/extension/ja/ganganonline/Dto.kt
@@ -0,0 +1,112 @@
+package eu.kanade.tachiyomi.extension.ja.ganganonline
+
+import eu.kanade.tachiyomi.source.model.SChapter
+import eu.kanade.tachiyomi.source.model.SManga
+import keiyoushi.utils.tryParse
+import kotlinx.serialization.Serializable
+import java.text.SimpleDateFormat
+
+@Serializable
+class NextData<T>(
+    val props: Props<T>,
+)
+
+@Serializable
+class Props<T>(
+    val pageProps: PageProps<T>,
+)
+
+@Serializable
+class PageProps<T>(
+    val data: T,
+)
+
+@Serializable
+class MangaListDto(
+    val titleSections: List<MangaSectionDto>?, // Popular/Finished
+    val sections: List<SearchSectionDto>?, // Search
+    val ongoingTitleSection: MangaSectionDto?, // GA
+    val finishedTitleSection: MangaSectionDto?, // GA
+)
+
+@Serializable
+class MangaSectionDto(
+    val titles: List<MangaDto>,
+)
+
+@Serializable
+class SearchSectionDto(
+    val titleLinks: List<MangaDto>,
+)
+
+@Serializable
+class MangaDto(
+    private val titleId: Int,
+    private val header: String?, // Popular/Finished
+    private val name: String?, // Search
+    private val imageUrl: String?,
+    val isNovel: Boolean?,
+) {
+    fun toSManga(baseUrl: String): SManga = SManga.create().apply {
+        url = "/title/$titleId"
+        title = header ?: name!!
+        thumbnail_url = baseUrl + imageUrl
+    }
+}
+
+@Serializable
+class PixivPageDto(
+    val ganganTitles: List<MangaDto>?,
+)
+
+@Serializable
+class MangaDetailDto(
+    val default: MangaDetailDefaultDto,
+)
+
+@Serializable
+class MangaDetailDefaultDto(
+    private val titleName: String,
+    private val author: String,
+    private val description: String,
+    private val imageUrl: String,
+    val chapters: List<ChapterDto>,
+) {
+    fun toSManga(baseUrl: String): SManga = SManga.create().apply {
+        title = titleName
+        author = this@MangaDetailDefaultDto.author
+        description = this@MangaDetailDefaultDto.description
+        thumbnail_url = baseUrl + imageUrl
+    }
+}
+
+@Serializable
+class ChapterDto(
+    private val id: Int,
+    val status: Int?,
+    private val mainText: String,
+    private val subText: String?,
+    private val publishingPeriod: String?,
+) {
+    fun toSChapter(mangaUrl: String, dateFormat: SimpleDateFormat): SChapter = SChapter.create().apply {
+        url = "$mangaUrl/chapter/$id"
+        name = mainText + if (!subText.isNullOrEmpty()) " - $subText" else ""
+        date_upload = publishingPeriod?.substringBefore("〜").let { dateFormat.tryParse(it) }
+    }
+}
+
+@Serializable
+class PageListDto(
+    val pages: List<PageDto>,
+)
+
+@Serializable
+class PageDto(
+    val image: PageImageUrlDto?,
+    val linkImage: PageImageUrlDto?,
+)
+
+@Serializable
+class PageImageUrlDto(
+    val imageUrl: String,
+)
diff --git a/src/ja/ganganonline/src/eu/kanade/tachiyomi/extension/ja/ganganonline/GanganOnline.kt b/src/ja/ganganonline/src/eu/kanade/tachiyomi/extension/ja/ganganonline/GanganOnline.kt
new file mode 100644
index 000000000..1c0ed6d2c
--- /dev/null
+++ b/src/ja/ganganonline/src/eu/kanade/tachiyomi/extension/ja/ganganonline/GanganOnline.kt
@@ -0,0 +1,127 @@
+package eu.kanade.tachiyomi.extension.ja.ganganonline
+
+import eu.kanade.tachiyomi.network.GET
+import eu.kanade.tachiyomi.source.model.Filter
+import eu.kanade.tachiyomi.source.model.FilterList
+import eu.kanade.tachiyomi.source.model.MangasPage
+import eu.kanade.tachiyomi.source.model.Page
+import eu.kanade.tachiyomi.source.model.SChapter
+import eu.kanade.tachiyomi.source.model.SManga
+import eu.kanade.tachiyomi.source.online.HttpSource
+import eu.kanade.tachiyomi.util.asJsoup
+import keiyoushi.utils.firstInstance
+import keiyoushi.utils.parseAs
+import okhttp3.HttpUrl.Companion.toHttpUrl
+import okhttp3.Request
+import okhttp3.Response
+import java.text.SimpleDateFormat
+import java.util.Locale
+
+class GanganOnline : HttpSource() {
+    override val name = "Gangan Online"
+    override val baseUrl = "https://www.ganganonline.com"
+    override val lang = "ja"
+    override val supportsLatest = false
+
+    private val dateFormat = SimpleDateFormat("yyyy.MM.dd", Locale.JAPAN)
+
+    override fun popularMangaRequest(page: Int): Request = GET("$baseUrl/rensai", headers)
+
+    override fun popularMangaParse(response: Response): MangasPage = searchMangaParse(response)
+
+    override fun searchMangaRequest(page: Int, query: String, filters: FilterList): Request {
+        if (query.isNotBlank()) {
+            val url = "$baseUrl/search/result".toHttpUrl().newBuilder()
+                .addQueryParameter("keyword", query)
+                .build()
+            return GET(url, headers)
+        }
+
+        val filter = filters.firstInstance<CategoryFilter>()
+        val url = baseUrl.toHttpUrl().newBuilder()
+            .addPathSegments(filter.toUriPart().removePrefix("/"))
+            .build()
+        return GET(url, headers)
+    }
+
+    override fun searchMangaParse(response: Response): MangasPage {
+        val url = response.request.url.toString()
+        val mangas = when {
+            "/search/result" in url -> {
+                val data = response.parseAsNextData<MangaListDto>()
+                data.sections?.flatMap { it.titleLinks }
+                    ?.filter { it.isNovel != true }
+                    ?.map { it.toSManga(baseUrl) }
+            }
+            "/rensai" in url || "/finish" in url -> {
+                val data = response.parseAsNextData<MangaListDto>()
+                data.titleSections?.flatMap { it.titles }
+                    ?.filter { it.isNovel != true }
+                    ?.map { it.toSManga(baseUrl) }
+            }
+            "/ga" in url -> {
+                val data = response.parseAsNextData<MangaListDto>()
+                val ongoing = data.ongoingTitleSection?.titles!!
+                val finished = data.finishedTitleSection?.titles!!
+                (ongoing + finished)
+                    .filter { it.isNovel != true }
+                    .map { it.toSManga(baseUrl) }
+            }
+            "/pixiv" in url -> {
+                val data = response.parseAsNextData<PixivPageDto>()
+                data.ganganTitles?.map { it.toSManga(baseUrl) }
+            }
+            else -> null
+        }
+        return MangasPage(mangas!!, false)
+    }
+
+    override fun mangaDetailsParse(response: Response): SManga {
+        return response.parseAsNextData<MangaDetailDto>().default.toSManga(baseUrl)
+    }
+
+    override fun chapterListParse(response: Response): List<SChapter> {
+        val mangaUrl = response.request.url.toString()
+            .substringBefore("/chapter")
+            .substringAfter(baseUrl)
+        val data = response.parseAsNextData<MangaDetailDto>().default
+
+        return data.chapters
+            .filter { it.status == null || it.status >= 4 }
+            .map { it.toSChapter(mangaUrl, dateFormat) }
+    }
+
+    override fun pageListParse(response: Response): List<Page> {
+        val data = response.parseAsNextData<PageListDto>()
+        return data.pages.mapIndexed { i, page ->
+            val imageUrl = (page.image ?: page.linkImage)!!.imageUrl
+            Page(i, imageUrl = baseUrl + imageUrl)
+        }
+    }
+
+    override fun getFilterList() = FilterList(
+        CategoryFilter(getCategoryList()),
+    )
+
+    private class CategoryFilter(private val category: Array<Pair<String, String>>) :
+        Filter.Select<String>("Category", category.map { it.first }.toTypedArray()) {
+        fun toUriPart() = category[state].second
+    }
+
+    private fun getCategoryList() = arrayOf(
+        Pair("連載作品", "/rensai"),
+        Pair("連載終了作品", "/finish"),
+        Pair("ガンガンpixiv", "/pixiv"),
+        Pair("ガンガンGA", "/ga"),
+    )
+
+    private inline fun <reified T> Response.parseAsNextData(): T {
+        val script = this.asJsoup().selectFirst("script#__NEXT_DATA__")!!.data()
+        return script.parseAs<NextData<T>>().props.pageProps.data
+    }
+
+    // Unsupported
+    override fun latestUpdatesRequest(page: Int): Request = throw UnsupportedOperationException()
+    override fun latestUpdatesParse(response: Response): MangasPage = throw UnsupportedOperationException()
+    override fun imageUrlParse(response: Response): String = throw UnsupportedOperationException()
+}