Sir Robert Knollys (or Knolles) (died 1521) was an English courtier in the service and favour of Henry VII and Henry VIII.
Sir Robert was the son of Robert Knollys and Elizabeth Troutbeck, paternal grandson of Sir Richard Knollys and Margaret D'Oyley, and maternal grandson of Sir John Troutbeck and Margaret Hulse.
In 1488 Knollys was one of Henry VII's henchmen, and late in that year was appointed to wait on ‘the king's dearest son the prince’ (Arthur). He received £5 ‘by way of reward’ for each of the three years 1488 to 1490, and when Henry VII met Archduke Philip in 1500, Knollys accompanied the English king as one of the ushers of the chamber. He continued in the same office under Henry VIII, and received an annuity of £20, on 15 November 1509, and a grant of Upclatford, called Rookes Manor, in Hampshire — part of the confiscated property of Sir Richard Empson — on 10 February 1510/11. On 9 July 1514 the usher and his wife were jointly granted the manor of Rotherfield Greys, near Henley-on-Thames, Oxfordshire, in survivorship, at an annual rental of a red rose at midsummer. The grant was confirmed on 5 January 1517/18 by letters patent for their own lives and that of one successor. Other royal gifts followed.
Robert Knollys died in 1521, and was buried in the church of St Helen's Bishopsgate. His will, dated 13 November 1520, was proved 19 June 1521. His widow, Letitia or Lettice, was daughter of Sir Thomas Penyston or Penystone, of Hawridge and Marsworth, both in Buckinghamshire, and Alice Bulstrode, and granddaughter of Sir Richard Penystone and Margaret Herris, and Richard Bulstrode and Alice Knyffe. After Robert Knollys's death she became the second wife of Sir Robert Lee, of Burston, Buckinghamshire, son of Richard Lee (died c.1500) and Joan Saunders (d.1516). Sir Robert Lee, by whom she had issue, died in 1539, when she became the second wife of Sir Thomas Tresham of Rushton, Northamptonshire, prior (under Queen Mary of England) of the Knights of St. John of Jerusalem. Her will, dated 28 June 1557, was proved 11 June 1558.