Were there any queens in ancient Greece?

Answer 1

From myth:

Eurydice was queen of Argon and grandmother to Perseus. Jocasta was queen of Thebes and both mother and wife of Oedipus. Medea was queen of Corinth and wife of Jason (although he later said she wasn't).

From history:

Olympia was queen of Macedon and the mother of Alexandra the Great. There were several Cleopatras who were queens of Egypt during the post-Alexandrian era. Gorgo was the queen of Sparta and wife of Leonides (from 300).

These are of course only a few.

Answer 2

As far as I know no Queen ruled any of the greek states without a King until the Byzantine empire where there were empresses (Theodora the Armenian,Theodora the Macedonian). Thus said, many queens actually ruled their kingdom under the pretext of their husbands. Most notably Arsenoe II of Egypt ,Gorgo and others.