The af Chapman, formerly the Dunboyne (1888–1915) and the G.D. Kennedy (−1923), is a full-rigged steel ship moored on the western shore of the islet Skeppsholmen in central Stockholm, Sweden, now serving as a youth hostel.

The ship was constructed by the Whitehaven Shipbuilding Company, located in Whitehaven, Cumberland (present-day Cumbria), and launched in February 1888. It was originally known as Dunboyne, after a town in County Meath, Ireland. Its maiden voyage was from Maryport, Cumberland to Portland Oregon, USA, and it subsequently made voyages between Europe, Australia and the west coast of America. On its arrival in Sweden in 1915 it was renamed G. D. Kennedy and when the Swedish Navy bought it in 1923 it was given its present name after the shipbuilder and Vice Admiral Fredrik Henrik af Chapman (1721–1808). The Navy used it as a training ship and as such it made several trips around the world before serving as a barracks during WW2. Its final voyage was in 1934.

In 1947 the Stockholm City Museum saved the ship from being broken up, and since 1949 af Chapman has been managed by the Svenska Turistföreningen (STF, Swedish Tourist Association). It serves as a youth hostel with 285 beds. During 2008 the ship underwent a comprehensive restoration. While the ship was being worked on in a drydock, the adjacent youth hostel Skeppsholmen remained open. Usually, the af Chapman and Skeppsholmen – not to be confused with the islet of the same name, on which both are situated – are run as a single hostel, with the af Chapman offering accommodation and Skeppsholmen housing the reception, a kitchen for guests, and other facilities. The ship is docked on the shore next to the Admiralty House,