Horrifying and darkly comic, Rosemary’s Baby was Roman Polanski’s Hollywood debut. This wildly entertaining nightmare, faithfully adapted from Ira Levin’s best seller, stars a revelatory Mia Farrow as a young mother-to-be who grows increasingly suspicious that her overfriendly elderly neighbors (played by Sidney Blackmer and an Oscar-winning Ruth Gordon) and self-involved husband (John Cassavetes) are hatching a satanic plot against her and her baby. In the decades of occult cinema that Polanski’s ungodly masterpiece has spawned, it has never been outdone for sheer psychological terror.
You can stream Rosemary's Baby (1968) free and legally on alltube, via the Internet Archive.
Yes — it is in the public domain and can be watched and shared freely.