Vice-Admiral Sir William Mitchell KCB (c. 1745 – 7 March 1816) was an officer of the British Royal Navy during the eighteenth and early nineteenth centuries.

His service was highly varied, including a circumnavigation of the world, command of a ship at the Battle of Camperdown in 1797 and a period as Sir James Saumarez's flag captain.

The first time that he appears in the historical record is in 1766, when he joined the Royal Navy ship HMS Dolphin under Captain Samuel Wallis.

In 1808 he was promoted to rear-admiral and continued to rise through the ranks during his years on shore, becoming a vice-admiral in 1813 and being made a Knight Commander of the Order of the Bath shortly before his death at Camberwell in Surrey on 7 March 1816.

Many years after his death, Sir John Ross wrote of him that he had "risen to the rank of rear-admiral by his good conduct, after having been flogged round the fleet for desertion".