William Sidney Walker (1795–1846) was an English Shakespearean critic.
Born at Pembroke in Wales, on 4 December 1795, he was the eldest child of John Walker, a naval officer, who died at Twickenham in 1811 from the effects of wounds received in action. The boy was named after his godfather, Admiral Sir Sidney Smith, under whom his father had served. His mother's maiden name was Falconer. William Sidney, always called Sidney, spent some years at a school at Doncaster, kept by his mother's brother, and with a private tutor at Forest Hill; he then entered Eton College in 1811. At Eton he learnt the whole of Homer by heart, and wrote Greek verse with facility. There, too, he began lifelong friendships with Winthrop Mackworth Praed and John Moultrie.
Walker, small, uncouth and absent-minded, was bullied at school. He was entered as a sizar at Trinity College, Cambridge, on 16 February 1814, but did not come into residence until the following year. He won the Craven scholarship in 1817, and the Porson prize for Greek verse in 1818, and he was admitted scholar of Trinity on 3 April of the latter year. Although his weak mathematics rendered his passing the examination for the degree of B.A. in 1819 difficult, he was elected for his classical attainments to a fellowship at his college in 1820. He maintained close relations with Praed and Moultrie, and formed a friendship with Derwent Coleridge.
In 1824 he was an unsuccessful candidate for the Greek professorship at Cambridge. He made no other effort to engage in educational work. While a fellow of Trinity he lived in seclusion in his college rooms, reading desultorily.
As an undergraduate Walker had religious doubts, and had applied for guidance to William Wilberforce. During 1818–19 Wilberforce wrote him letters in which he endeavoured to confirm his beliefs. The influence of Charles Simeon helped him for a time; but he deemed himself disqualified by his sceptical views regarding eternal punishment from taking holy orders. As a consequence he resigned his fellowship in 1829.