Clayton Graham Blackmore (born 23 September 1964) is a Welsh former international footballer. He was a combative player known for his attacking free kicks and a utility player who excelled in defence, but could play equally well in midfield.
Blackmore began his professional career at Manchester United in 1982, having progressed through the club's youth ranks. After twelve years and 186 league appearances, he switched to Middlesbrough on a free transfer, and made 53 league appearances in five years, whilst also having a brief loan spell at Bristol City in 1996. Having left Middlesbrough in 1999, he had short spells at Barnsley, Notts County and Leigh RMI over the next couple of seasons, before a much longer stint at Bangor City commenced in 2000. He left Bangor City in 2006 (after a brief stint as player-manager), having made 176 league appearances for the club, and, after spending a season with Porthmadog (where he was also player-manager), switched to Neath Athletic in 2007, where he made a further 22 league appearances before retiring in 2010. Internationally, Blackmore won 39 caps for Wales between 1985 and 1997.
He was given his debut for United on 16 May 1984 by manager Ron Atkinson, in their 2–0 league defeat against Nottingham Forest at the City Ground. He made a solitary league appearance the following season, although in 1985–86 he scored three goals in 12 league games, but he did not get a serious run in the side until the 1987–88 season, by which time Alex Ferguson was United's manager, when he played 22 league games and scored three goals. 1988–89 saw Blackmore enjoy even more first team opportunities as he played 28 times in the league.
In 1991, he won a European Cup Winners' Cup medal with United, and in 1990 he won the FA Cup with them. He was United's regular left-back in the 1990–91 season, but when Paul Parker signed in the close season, Denis Irwin was switched to left-back and Blackmore returned to his familiar pattern of alternating between different positions, although he did enjoy a good run at right-back when Parker was injured.
Blackmore collected an FA Premier League title medal in 1992–93, although he was no longer a regular player at the club, often coming on a substitute or standing in as a full-back or on the flanks on the few occasions he did start a game. A succession of injuries meant that he was unable to play in the 1993–94 season, and competition throughout the team was growing.
In the days of 1–11 numbering of shirts (with players not being assigned the same shirt number for every game of the season), Blackmore's versatility meant that he wore every shirt number from 2 to 11, as well as some of the shirt numbers from 12 to 16 as a substitute. He was assigned with the number 15 when squad numbers were introduced by the FA Premier League for the 1993–94 season, but did not play any first team games that season.
He joined Middlesbrough on a free transfer for the 1994–95 season after spending more than a decade at Old Trafford. He was signed by newly appointed player-manager Bryan Robson, who had just headed to Teesside from United. He helped them win promotion to the Premier League as Division One champions in his first season on Teesside, playing in 30 League games and scoring two goals. He also appeared in Middlesbrough's 1997 FA Cup Final defeat by Chelsea. Whilst at Boro he had a loan spell with Bristol City.
On 3 September 2018, Clayton Blackmore enters the coaching staff of Dynamo Brest Academy. The contract is signed until March 2021. 
He won 39 caps for Wales. He made his senior debut for the national side on 26 February 1985, in a 1–1 friendly draw with Norway, and his final appearance for the Welsh side came on 29 March 1997.
- Premier League: 1992–93
- FA Cup: 1989–90
- FA Charity Shield: 1990 (shared)
- European Cup Winners' Cup: 1990–91
- European Super Cup: 1991