Sir John Williams, 1st Baronet GCVO (6 November 1840 – 24 May 1926), was a Welsh physician, who attended Queen Victoria and was raised to the baronetcy by her in 1894. He is remembered chiefly for his contribution to the collection of the National Library of Wales. He resided for part of his life at Plas Llanstephan, Carmarthenshire, a house he acquired by lease.