Ian Douglas Neilson (born 20 October 1954) is a South African civil engineer and politician who currently serves as Deputy Mayor of Cape Town after having taken the office on 27 May 2009. He previously served as the Mayoral Committee Member for Finance from 2006 until 2016 and Executive Councillor for Safety and Health from 2000 until 2002. He has served as acting Mayor of Cape Town on two brief occasions in 2018, in May and currently from 31 October until Dan Plato is sworn in on 6 November.