|Birth name||William Iain Henderson|
|Date of birth||21 February 1992|
|Place of birth||Craigavon, Northern Ireland|
|Height||1.98 m (6 ft 6 in)|
|Weight||117 kg (18 st 6 lb; 258 lb)|
|School||Belfast Royal Academy|
|University||Queen's University Belfast|
|Rugby union career|
Henderson started his rugby career at Belfast Royal Academy where he excelled at all age levels up to, and including the school's 1st XV when he guided them to the final of the Ulster Schools' Cup in 2010.
Henderson represented Ireland at U19 level and at U20 level. During the time playing for the Ireland U20 side, he assisted in securing fifth place in the 2012 U20 World Championships helping the team beat South Africa, England and France.
Henderson received a call up for the Ireland national rugby union team on 28 October 2012. On 10 November 2012, he made his senior debut for Ireland in the defeat to South Africa in Dublin. Henderson was called up for the Lions in the 2017 British and Irish Lions tour to New Zealand.
- Ulster Iain Henderson Profile Archived 2012-10-29 at the Wayback Machine
-  Additional Players Drafted Into Ireland Squad
- "Pressure increases on Declan Kidney as limp second half exposes Ireland's limitations". Irish Independent. 12 November 2012. Retrieved 13 November 2012.
- "All 30 of Ireland's Grand Slam contributors rated - but one man comes out on top". Irish Independent. 20 March 2018. Retrieved 22 March 2018.