Timothy John Nielsen (born 5 May 1968) is a former South Australia state cricketer and formerly the head coach of the Australian cricket team. Nielsen played 101 first-class matches for his state between 1990–91 and 1998–99. Nielsen was confirmed as John Buchanan's replacement as the coach of Australia on 5 February 2007. Nielsen, who became the hot favourite when Tom Moody withdrew from contention, took over the role after the 2007 Cricket World Cup.