Ryan went to school at CBS Nenagh and played all his underage rugby with Nenagh Ormond, representing Munster and Irish Youths, before moving to St Munchin's College in Limerick, where he was a key member of the side that won the Munster Schools Rugby Senior Cup in 2002.

[13][14] On 19 May 2017, it was announced that Ryan would be leaving Munster upon the conclusion on the 2016–17 season to join French Top 14 side Racing 92.

[15] A neck hernia ruled Ryan out until the end of November 2017,[16] though he made his Racing debut on 3 December 2017[17] and started against his former club Munster on 14 January 2018.

[18] Ryan featured as a replacement for Racing 92 in the 2020 European Rugby Champions Cup Final against English club Exeter Chiefs on 17 October, which the Parisian side narrowly lost 31–27.

[19] Ryan's final game for Racing 92 was their 19–6 defeat against Ronan O'Gara's La Rochelle in the semi-finals of the 2020–21 Top 14 season on 18 June 2021.

He made his debut for the Irish national team on 22 November 2008 in a test against Argentina in Croke Park, Dublin.

[28] He made his first start for Ireland in the World Cup warm-up against Scotland on 6 August 2011, as well as playing against France and England.

[30] He came off the bench against Wales, Italy and France, and made his first Six Nations start in the Round 4 game against Scotland, in which he was named man of the match.

Ryan continued to hold down the Ireland number 5 jersey going into the 2013 Six Nations Championship, starting against Wales,[32] England[33] Scotland,[34] France,[35] and Italy.

[53][54][55][56] Upon the conclusion of the 2020–21 season, Ryan, who hadn't been offered a contract extension by Racing 92, rejected offers from Pro D2 clubs to continue his playing career and retired, joining the coaching team at La Rochelle, where Ryan's former Munster teammate and Racing 92 coach Ronan O'Gara was director of rugby.

[1] Ryan was part of the coaching setup at La Rochelle that won the 2021–22 European Rugby Champions Cup beating Leinster in the final 24-21.

[57] The following year, La Rochelle repeated the achievement by winning 2022–23 European Rugby Champions Cup, this time beating Leinster 27-26 at the Aviva Stadium.