Hamlet Winstanley was an English painter and engraver.

Winstanley was born in Warrington, Lancashire, the second son of William Winstanley, a tradesman. In 1707 he was placed under the tuition of Samuel Shaw, rector of the parish and master of the Boteler free grammar school. John Finch, rector of Winwick and brother of the Earl of Nottingham, gave him access to his collection of paintings, and enabled him to study in London at the academy of painting, founded in 1711 in Great Queen Street, Lincoln's Inn Fields. He remained in London for three years, having the personal attention of Sir Godfrey Kneller.

Winstanley returned to Warrington in 1721 with a commission to paint the portrait of Sir Edward Stanley. Its success led to his introduction to James Stanley, 10th Earl of Derby, and the earl ordered him to come and paint for him at his seat at Knowsley Hall. During the next two years he painted landscapes and portraits, including one of the earl. He was in Rome from 1723 to 1725.

He spent his later years at Warrington, where he built Stanley Street, and named it after his patrons at Knowsley. He died at Warrington on 18 May 1756. His collections of copper-plates and prints are stated by Horace Walpole to have been sold by auction at Essex House on 18 March 1762.

There are sketches of Rome and studies of antique figures drawn by Winstanley. The British Museum purchased two fine examples of pen and wash drawings by Winstanley in 1870. He executed large copies of the Three Graces by Raphael, in the Farnesina Palace at Rome, and of the Triumph of Bacchus by Annibale Caracci, in the Farnese Palace. Etchings from pictures by old masters (including Ribera, Rembrandt, Vandyck, Carlo Dolci, Tintoretto, Titian, Rubens, Snyders, and Salvator Rosa) in the possession of the Earl of Derby were bound together in a portfolio known as the Knowsley Gallery.

Winstanley executed portraits of the Stanleys, of John Blackburne of Orford Hall, of Samuel Peploe, and Jonathan Patten of Manchester. Several of his portraits were etched or engraved; that of the Earl of Derby was retouched by Gerard Van der Gucht; and the portrait of Edward Waddington, painted in 1730, was engraved in mezzotint by John Faber Junior. Some of his landscape and other subjects were at Knowsley, and Winstanley also made etchings of Sir James Thornhill's paintings in the dome of St Paul's Cathedral.