King Roger (Król Roger, op. 46) is a Polish opera in 3 acts, with music by Karol Szymanowski and the libretto by the composer himself and Jarosław Iwaszkiewicz, the composer's cousin. The opera received its world premiere on 19 June 1926 in Warsaw, Poland, with the cast including the composer's sister, the soprano Stanisława Korwin-Szymanowska, as Roxana.

The opera originated from Szymanowski's enthusiasm for Mediterranean culture as a melting pot of different peoples and religions. He spent much time travelling in that area in 1911 and in 1914, and shared his love of the region with Iwaszkiewicz. In the summer of 1918 at Odessa, Ukraine, Szymanowski and Iwaszkiewicz conceived the project, and composed the opera over the period of 1918 to 1924. Szymanowski's lost novel Efebos dealt with mystical themes similar to those that inspired this work.

Jim Samson has placed King Roger in a musico-psychological analysis of Szymanowski's compositional struggles. Alistair Wightman has briefly discussed Szymanowski's stylised treatment of Arabic musical idioms in the score. Stephen Downes has analysed in detail the themes of "duality" and "transformation" expressed in the music of the opera.