A trailer for towing by a bicycle is disclosed comprising a tow arm adapted for coupling by a hitch to the bicycle. The tow arm is pivotally coupled to an upper portion of the trailer frame and can be collapsed against the frame. The frame can comprise plural frame sections that can also pivot to a collapsed position and a lower shelf foldable to a collapsed position as well. Locking elements can be provided for selectively locking the trailer components against relative pivoting motion. One or more actuators for selectively locking and unlocking the frame components can be provided. One such actuator can simultaneously unlock first and second transversely spaced apart hinge elements. The hitch can comprise a flexible coupling that provides torsional resistance against rolling motion of the trailer, particularly when the trailer is mounted to a seat post or other location above the rear wheel of the bicycle. The flexible hitch coupling can provide a progressively increasing torsional resistance to such rolling while allowing pivoting of the trailer relative to the bicycle as the bicycle is steered and flexing to accommodate variations in pitch between the bicycle and trailer.