Lachlan Renshaw (born 2 April 1987 in Sydney, Australia) is a middle-distance track and field athlete and is the 2010 Australian Champion over 800 metres.

He represented Australia at the 2008 Beijing Olympics, finishing sixth in his heat in a time of 1:49.19.

Lachlan has also competed at the international level at the 2006 World Junior Championships (3rd in his semi-final), as well as the 2007 and 2009 World University Games, finishing fifth in the 800 m in the latter event.

Lachlan attended Sydney Grammar School and was a winner of the Open 800 m Championship event at the AAGPS Athletics Competition for four years running, setting the 800 m record of 1:50.63 in his final year of school.

He was further a member of the 4 × 400 metres relay team which holds the AAGPS record.