gynocracy (alt spelling gynecocracy) fits what the OP is asking. From the Oxford English Dictionary
Women as the ruling class
Alt. gynecocracy, OED
Government by a woman or women; female rule or mastery;
depreciatingly, petticoat government.
Quotation from the OED:
1864 Macmillan's Mag. July 219 From a gynocracy..heaven save us
and all Christian communities!
The oldest form is gynarchy, "government by women or a woman". See Etomonline:
gynarchy: government by women or a woman," 1570s, from Greek gyne "woman, wife," from PIE *gwen- "woman" (see queen) + -arkhe "rule" (see archon).
Synonymous gynaecocracy (from Greek gynaikokratia) and gyneocracy are
attested from 1610s; gynocracy is from 1728.
matriarchy is close, but not quite what the OP is asking for. From the OED
A form of social organization in which the mother or oldest female is
the head of the family, and descent and relationship are reckoned
through the female line; government or rule by a woman or women. Also
(in Cultural Anthropol.): a culture or community in which such a
system prevails; a family, society, organization, etc., dominated by a
woman or women.
The difference appears to be that in a matriarchy, the females of the family line hold power in the family and by extension a prominent place in the society, whereas in a gynocracy women hold power as individuals, not as family elders who are women.