Simon Ross Harmer (সাইমন হারমার) is a South African international cricketer. He plays for South Africa primarily as an off-break bowler but is also a capable lower order batsman. He plays domestic cricket in South Africa for Titans, and in England for Essex.

Harmer debuted for Warriors in the 2010–2011 first class season against the Cape Cobras claiming 5/98 in the first innings and 1/53 in the second innings to go along with his 46 and 69 runs with the bat. He became a regular fixture in Warriors side in the 2011–2012 side, ending the season as leading wicket taker in his full rookie season, claiming 44 wickets.

These performances earned him a call up for the 3rd Test against West Indies in 2014/15, where he made his Test match debut for South Africa against the West Indies on 2 January 2015 at Newlands, Cape Town. He took his debut Test wicket by bowling Devon Smith in the last over before the lunch break on day one and ended the innings with figures of 3/71 from 26 overs.

Ahead of the 2017 season, Harmer signed for Essex County Cricket Club as a Kolpak player. In June, in the 2017 County Championship, Harmer took 9 wickets for 95 runs in the second innings against Middlesex. He was the first bowler for Essex to take nine wickets in an innings since Mark Ilott in 1995, and he finished with career-best match figures of 14 for 172.

Harmer continued his form and took the wicket which confirmed Essex as Champions in the win against Warwickshire. Harmer finished the 2017 season with the second-highest haul in the Country in terms of wickets taken, with 72 wickets at 19.19. Although neither he, nor his team, hit the same heights in 2018, he still managed 57 wickets at 24.45 each and provided useful runs batting at number eight in the batting order.