Queenborough is a town on the Isle of Sheppey in the Swale borough of Kent in South East England. Queenborough is two miles south of Sheerness. It grew as a port near the Thames Estuary at the westward entrance to the Swale where it joins the River Medway. It is in the Sittingbourne and Sheppey parliamentary constituency. Queenborough Harbour offers moorings between the Thames and Medway.