Kidwelly (Welsh: Cydweli) is a town in Carmarthenshire, Wales, lying on the River Gwendraeth above Carmarthen Bay.

Attractions in the town include Kidwelly Castle , founded in 1106, a fourteenth century bridge and gate, the former quay (now a nature reserve) and an industrial museum .

Near the castle, in a field known as "Maes Gwenllian", was a battle of 1136, in which Princess Gwenllian, sister of Owain Gwynedd, led her husband's troops into battle against a Norman army during his absence. She is believed to have been killed either during the battle or shortly afterwards.