The present invention relates to the field of boat trailers, and in particular, to boat trailers with rotatable support structures. The boat trailer includes a front end configured for hitching to a towing vehicle, a rear end, a wheel assembly disposed between the front and rear ends for rolling engagement with the ground and a support frame assembly carried on the wheel assembly. The support frame assembly has a lower base frame portion and an upper carousel frame portion superimposed on, and pivotally connected to, the base frame portion. The carousel frame portion is configured to support a boat thereon. Also provided is a support frame lifting assembly connected to the support frame assembly and the wheel assembly. The support frame lifting assembly is operable to raise at least a portion of the support frame assembly above the wheel assembly so as to permit rotation of the carousel frame portion relative to the base frame portion. Advantageously, this boat trailer may be used to reorient a boat carried on the support frame assembly for bow-first launching into water.