William John "Billy" Spiller (8 July 1886 – 9 June 1970), was a Welsh rugby union player and cricketer. His greatest achievements were in rugby, where he won ten international caps at centre for Wales between 1910 and 1913, but his short first-class cricket career was also notable as he was the first man to score a century for Glamorgan after their elevation to first-class status in the 1921 season.