The AEC 691T was a one-off experimental three-axle double deck trolleybus chassis manufactured by AEC. In 1932, the Underground Electric Railways Company of London commissioned AEC to build an extended version of the AEC 663T.^[1]

It was bodied by the London General Omnibus Company's Chiswick works entering service with London United Tramways in March 1933. It had a front mounted door just behind the front axle, as opposed to a rear platform. It operated demonstration trips in Bournemouth in 1933 and Brighton in 1936.^[1]