Which tragic king from classical mythology unknowingly killed his father and married his mother?

The figure from classical mythology who tragically fulfilled a prophecy by unknowingly slaying his father and marrying his mother is Oedipus. Born to King Laius and Queen Jocasta of Thebes, a prophecy foretold that their son would kill his father and marry his mother. To avert this terrible fate, they abandoned the infant, piercing his ankles and leaving him to die on a mountainside. However, a shepherd took pity on the child, who was then adopted by the childless King Polybus and Queen Merope of Corinth, and named Oedipus, meaning "swollen foot".

Unaware of his true parentage, Oedipus later consulted the Oracle at Delphi, which reiterated the prophecy that he was destined to kill his father and marry his mother. Believing Polybus and Merope to be his biological parents, he fled Corinth to prevent the prophecy's fulfillment. On his journey, he encountered an older man and his retinue at a crossroads, leading to a quarrel in which Oedipus killed the man, who was, unbeknownst to him, King Laius, his birth father. Continuing to Thebes, he famously solved the riddle of the Sphinx, freeing the city from its torment. As a reward, he was offered the vacant throne and the hand of the recently widowed queen, Jocasta, thereby unknowingly marrying his own mother.

Years later, a plague afflicted Thebes, and the truth of Oedipus's lineage and actions was revealed through a relentless investigation. Upon discovering the horrific truth, Jocasta took her own life, and a grief-stricken Oedipus blinded himself, unable to bear witness to the consequences of his unwitting deeds. This powerful and enduring myth, famously dramatized in Sophocles' "Oedipus Rex," has had a profound impact on Western culture, lending its name to Sigmund Freud's psychoanalytic concept of the Oedipus complex and inspiring numerous adaptations across various art forms, including significant cinematic interpretations like Pier Paolo Pasolini's 1967 film.