Siemowit II of Rawa (pl: Siemowit II rawski; 1283 – 18 February 1345), was a Polish prince member of the House of Piast, Duke of Warsaw and Liw during 1310-1313, after a new division with his brothers since 1313 ruler over Rawa Mazowiecka, Sochaczew, Zakroczym, Gostynin, Ciechanów and Wizna, regent of Płock during 1336–1340.
He was the eldest son of Bolesław II of Płock and his first wife Gaudemantė (Sophia), the daughter of Grand Duke Traidenis of Lithuania. He was probably named after his paternal grandfather, Siemowit I.