Thomas Alun Lockyer (born 3 December 1994) is a Welsh professional footballer who plays as a centre back for EFL Championship club Luton Town and the Wales national team.

During a Premier League match on 16 December 2023, Lockyer suffered a cardiac arrest on the pitch; he was resuscitated and was later fitted with an implantable cardioverter-defibrillator.

[7] Lockyer then signed a scholarship for Bristol Rovers in 2011[8] and went on to make his debut on 12 January 2013, replacing Ellis Harrison, 85 minutes into a 3–0 win over Fleetwood Town at Highbury Stadium.

[19] After playing every minute of 43 league appearances in the 2019–20 season and missing only three matches due to suspension, Lockyer triggered a relegation release clause in his contract in August 2020, allowing him to join another club for free.

[28] On 16 May 2023, he scored Luton's all important second goal to defeat Sunderland and send the club to Wembley Stadium for the Championship play-off final.

[29] Lockyer was in the starting line-up for the 2023 Championship play-off final against Coventry City, but was stretchered off the pitch after collapsing in the 11th minute of the first half and taken to hospital.

[30] On 31 May, it was confirmed by the club that he would be leaving hospital the following day,[31] with a follow-up report a week later stating that Lockyer had suffered atrial fibrillation of the heart, but he was given the all clear to resume his playing career following surgery.

[32] On 12 August 2023, Lockyer captained Luton in the club's first Premier League match as they lost 4–1 to Brighton & Hove Albion on the opening day of the 2023–24 season.

[36] Bournemouth player Philip Billing was the first person to summon assistance to the defender before the arrival of the medical staff,[37] who managed to resuscitate him in two minutes.

[39] In December 2024, just one week before his scheduled return to development squad action, he suffered ankle ligament damage in training, requiring surgery.