Sonnet 20 is one of the best-known of 154 sonnets written by the English playwright and poet William Shakespeare. Part of the Fair Youth sequence, the subject of the sonnet is widely interpreted as being male, thereby raising questions about the sexuality of its author. In this sonnet the beloved's beauty is compared to both a man's and a woman's.

William Shakespeare (1564–1616) wrote sonnets on a variety of themes. When discussing or referring to Shakespeare's sonnets, it is almost always a reference to the 154 sonnets that were first published all together in a quarto in 1609. However, there are six additional sonnets that Shakespeare wrote and included in the plays Romeo and Juliet, Henry V and Love's Labour's Lost. There is also a partial sonnet found in the play Edward III.