Sir Thomas Knollys (also Knolles, died 1435) was Sheriff of London in 1394 and Lord Mayor of London in 1399 and 1410.
Knollys was a member of the Grocers' Company and an alderman, acting as Sheriff of London in 1394 and Lord Mayor of London in 1399 and 1410. He directed in 1400 the rebuilding of the Guildhall, and he also rebuilt St. Antholin's Church in Watling Street, where he was buried with his wife Joan. His will, dated 20 May 1435, was proved 11 July 1435 at Lambeth, where it is still preserved. He was MP for the City of London as one of the two aldermanic representatives.
Knollys was a forebear of Robert Knollys (great-great-grandson) and Francis Knollys (Robert's son).
Knollys is said by Dugdale to have been descended from Sir Robert Knollys or Knolles (d 1407), the soldier, but, according to Sidney Lee in the Dictionary of National Biography, this is an error. Discussing Francis Knollys, Lee states: "Sir Francis's pedigree cannot be authentically traced beyond Sir Thomas Knollys ... from whom Sir Francis's father was fifth in descent".