Janusz II of Płock (pl: Janusz II płocki; ca. 1455 - 16 February 1495), was a Polish prince member of the House of Piast in the Masovian branch. He was a Duke of Warsaw, Nur, Łomża, Liw, Ciechanów, Wyszogród and Zakroczym during 1454-1471 jointly with his brothers (under regency until 1462), Duke of Płock, Płońsk, Zawkrze and Wizna during 1462-1471, and after the division of the paternal domains in 1471, sole ruler over Ciechanów and Łomża, since 1475 also ruler over Płock, Płońsk, Zawkrze and Wizna, since 1484 ruler over Błonie, Tarczyn and Kamieniec, since 1489 ruler over Wyszogród.