Lieutenant Daniel Southwell (c. 1764 – 21 August 1797) was an officer of the Royal Navy, who as a midshipman was part of the crew of HMS Sirius when it sailed with the First Fleet to found a penal colony in Botany Bay. He kept a journal and corresponded with his mother, Jane Southwell, and uncle, the Reverend Weeden Butler. This correspondence is held in the British Museum with copies held in Mitchell Library, New South Wales.