Title: List of Manchester United F.C. managers
Content:   Manchester United Football Club is a professional football club based in Old Trafford, Greater Manchester, England. The club was formed in Newton Heath in 1878 as Newton Heath LYR F.C., and played their first competitive match in October 1886, when they entered the First Round of the 1886–87 FA Cup. The club was renamed Manchester United F.C. in 1902, and moved to Old Trafford in 1910. From the beginning of the club's official managerial records in 1892 to the start of the 2018–19 season, Manchester United have had 22 full-time managers. The current manager is Ralf Rangnick who took over as interim manager from caretaker Michael Carrick on 3 December 2021, himself replaced Ole Gunnar Solskjær on 21 November 2021. The longest-serving and most successful person to manage Manchester United is Sir Alex Ferguson, who won 13 Premier League titles, five FA Cups, four League Cups, 10 Community Shields, two UEFA Champions League titles, one UEFA Cup Winners' Cup, one UEFA Super Cup, one Intercontinental Cup and one FIFA Club World Cup in his managerial reign of more than 26 years.
Title: List of Manchester United F.C. records and statistics
Content: First full-time manager: Jack Robson – Robson was manager of Manchester United for 6 years and 10 months, starting on 28 December 1914, before pneumonia forced his retirement in October 1921. ; Longest-serving manager: Sir Alex Ferguson – 26 years, 194 days (1,500 matches; 6 November 1986 to 19 May 2013) 
Title: Alex Ferguson
Content:  league championships, four Scottish Cups and the UEFA Cup Winners' Cup in 1983. He briefly managed Scotland following the death of Jock Stein, taking the team to the 1986 World Cup. Ferguson was appointed manager of Manchester United in November 1986. During his 26 years with Manchester United he won 38 trophies, including 13 Premier League titles, five FA Cups, and two UEFA Champions League titles. He was knighted in the 1999 Queen's Birthday Honours list for his services to the game. Ferguson is the longest-serving manager of Manchester United, having overtaken Sir Matt Busby's record on 19 December 2010. He retired from management at the end of the 2012–13 season, having won the Premier League in his final season.
Title: List of longest managerial reigns in association football
Content:   The longest managerial reign in association football belongs to Englishman Fred Everiss, who was manager of Football League team West Bromwich Albion for over 45 years, starting his reign in 1902 and ending when he retired in 1948. The longest reign in the post-war era (post 1946) belongs to Frenchman Guy Roux, who managed Auxerre in three separate reigns totalling 44 years, taking them from France's fifth division to become Ligue 1 champions in 1995. Managerial reigns in football have decreased since the 1960s, and by 2015, the average spell in England's top four divisions was 1.23 years. Managers such as Pep Guardiola and Béla Guttmann have been proponents of a "three-year rule", as has football journalist and author Jonathan Wilson, who writes that managers can succumb to a "fatalistic idealism" beyond this period, describing it as similar to a Greek tragedy.
Title: Hereford United F.C.
Content:  Graham Turner was the longest serving Hereford United manager and was also second to Sir Alex Ferguson as the longest serving manager in the English football league, having completed almost 14 seasons at the club. The statistics of Hereford United's four most successful managers from the 1972–73 season onwards are shown below. Statistics include league matches only and are correct as of 7 May 2011.
Title: History of Manchester United F.C. (1986–2013)
Content:  manager of Manchester United after 27 years, with David Moyes of Everton being announced as his successor the next day. Ferguson remains as a director and ambassador for the club. On 19 May 2013, Ferguson managed Manchester United for the last time in the only 5–5 draw of his career, at West Bromwich Albion. Ferguson retired as the most decorated manager in the history of football. During his last eight years at United, he won 15 trophies: five Premier League titles, three Football League Cups, five FA Community Shields, one UEFA Champions League, and one FIFA Club World Cup.
Title: List of Manchester United W.F.C. records and statistics
Content: First full-time manager: Casey Stoney – Stoney was named manager in June 2018. It was the former England international's first managerial role. She had previously worked as a member of Phil Neville's England backroom staff. ; Longest-serving manager: Casey Stoney – 2 years, 343 days (77 matches) (8 June 2018 to 16 May 2021) 
Title: 2012–13 Manchester United F.C. season
Content:  2012, followed by a 1–0 win in the FA Cup Sixth Round Replay on 1 April 2013. In Europe, United were knocked out of the Champions League at the Round of 16 stage after losing 3–2 on aggregate to Real Madrid. On 8 May 2013, United's long time manager, Sir Alex Ferguson announced that he would retire from his position as manager of Manchester United after 26 and a half years in charge, making him the longest-serving manager of any English club by this stage. He had won 38 trophies during that time – more than any other manager in the history of football – and at 71 was the oldest serving manager currently in the Premier League or Football League. The next day, Manchester United announced that David Moyes of Everton would take over from Ferguson at the beginning of the 2013–14 season.
Title: List of Newcastle United F.C. managers
Content:  Newcastle United Football Club is an English football club based in Newcastle upon Tyne, Tyne and Wear, North East England. Since 1930, there have been 33 official managers, the most recent being Eddie Howe, who was appointed on 8th November 2021. Statistically, the club's most successful manager is Chris Hughton, with a win percentage of 59.38. The club's longest-serving manager was Stan Seymour, who had three spells managing the club from 1939 to 1958, totalling almost fourteen years, while the most successful manager was Joe Harvey, who won five trophies (albeit that four were minor trophies) and also had the longest uninterrupted spell as manager, lasting thirteen years from 1962 to 1975. All but three of the club's managers – Tom Mather, Norman Smith and Osvaldo Ardiles – have managed the club in the top-flight.
Title: Football records and statistics in England
Content: Longest-serving manager at one club: Fred Everiss, 46 years (West Bromwich Albion 1902–1948) ; Shortest-serving manager at one club (excluding caretakers): Leroy Rosenior, 10 minutes (Torquay United, 17 May 2007) ; Most trophy wins: Sir Alex Ferguson, 38 (Manchester United) ; Most League title wins: Sir Alex Ferguson, 13 (Manchester United) ; Most FA Cup wins: Arsène Wenger, 7 (Arsenal) ; Most League Cup wins: 4, joint record: ; Brian Clough with Nottingham Forest ; Sir Alex Ferguson with Manchester United ; Pep Guardiola with Manchester City ; José Mourinho with Chelsea (3) and Manchester United (1) ; Most FA Charity/Community Shield wins: Sir Alex Ferguson, 10 (9 outright, 1 shared) (Manchester United) ; Most Intercontinental Cup / FIFA Club World Cup wins: Sir Alex Ferguson, 2 (Manchester United) ; Most European Cup / UEFA Champions League wins: Bob Paisley, 3 (Liverpool)* ; Most Inter-Cities Fairs Cup / UEFA Cup / Europa League wins: Don Revie, 2 (Leeds United) ; Most top-flight League game wins: Sir Alex Ferguson, 625 games (Manchester United)''' ; Most European Cup / UEFA Champions League game wins: Sir Alex Ferguson, 110 games (Manchester United)''' 

Question: who is the longest serving manager in manchester united history?
Answer: Sir Alex Ferguson.