I know the Enterprise 1701 had captains before Kirk, but did Kirk captain any ship before Enterprise?
The OP's question is open to interpretation. Is he's asking if Kirk had ever held the rank of Captain aboard a prior position or is he asking if Kirk ever held a prior command (mostly likely a ship) before the Enterprise?
I think it unlikely that Kirk was a Captain before being assigned the Enterprise,
but the evidence suggests he has had a prior command before the Enterprise.
He couholdover held the rank of Commander and still have captained a previous ship.