Joint work with Ailsa Keating (Cambridge). We prove the homological mirror symmetry conjecture of Kontsevich for K3 surfaces in the following form: The Fukaya category of a projective K3 surface is equivalent to the derived category of coherent sheaves on the mirror, which is a K3 surface of Picard rank 19 over the field of formal Laurent series. This builds on prior work of Seidel (who proved the theorem in the case of the quartic surface), Sheridan, Lekili--Ueda, and Ganatra--Pardon--Shende.I will try to keep prerequisites to a minimum, in particular, I will not assume prior knowledge of the Fukaya category