Southgate made his debut for England as a substitute against Portugal in December 1995 under the management of Terry Venables. Southgate played every minute of their matches as hosts England reached the semi-final of UEFA Euro 1996, in which they faced Germany. The match was determined in a penalty shoot-out; Southgate’s penalty was saved, and England were eliminated. Southgate managed to make light of his blunder later that year by appearing in an advert for Pizza Hut, also featuring Stuart Pearce and Chris Waddle, who had missed crucial penalties at the 1990 FIFA World Cup.

Southgate attended Pound Hill Junior School and Hazelwick School in Crawley, West Sussex. He married Alison Bird in July 1997 at the St Nicholas’ Church in Worth; the couple have two children.

Southgate also played in the 1998 FIFA World Cup and UEFA Euro 2000. His 50th cap came in a 1–1 draw with Portugal at Villa Park in September 2002. On 11 June 2003, he played the full 90 minutes in a 2–1 Euro 2004 qualifying win over Slovakia at his club ground of the Riverside Stadium, competing against Middlesbrough’s striker Szilárd Németh.

Southgate was capped 57 times for England and scored twice. His first goal came on 14 October 1998 against Luxembourg in a Euro 2000 qualifier, his second on 22 May 2003 against South Africa in a friendly. He is Aston Villa’s most capped England player, having played 42 of his 57 internationals whilst with Villa.

On 11 July 2001, Southgate signed for Middlesbrough for a £6.5 million fee. He joined on a four-year deal and was the first signing by Steve McClaren, whom he knew as an England coach.

In July 2002, after Paul Ince left for Wolverhampton Wanderers, Southgate was appointed the new Middlesbrough captain. On 29 February 2004, he became the first Boro skipper in their 128-year history to lift a trophy, as they defeated Bolton Wanderers in the 2004 Football League Cup Final at the Millennium Stadium.

In 2003, Southgate and his close friend Andy Woodman co-wrote Woody & Nord: A Football Friendship. This book describes an enduring friendship forged in the Crystal Palace youth team that has survived Southgate and Woodman’s wildly differing fortunes in the professional game. The book won the Sports Book of the Year award for 2004 from the National Sporting Club (now the British Sports Book Awards).

Southgate rejected media rumours that he was set to move to Manchester United following Rio Ferdinand’s ban for missing a drug test in January 2004. He later committed his final playing years to Middlesbrough, signing until 2007. His final appearance as a professional player was in the 2006 UEFA Cup Final against Sevilla, which Boro lost 4–0 at the Philips Stadion in Eindhoven.

Southgate was handed his first managerial role at Middlesbrough in June 2006 after Steve McClaren had left to manage England. His appointment drew controversy as he did not have the required coaching qualifications (the UEFA Pro Licence) to manage a top-flight club. He was allowed to stay on as manager, however, by the Premier League in November 2006; Middlesbrough successfully argued that, because Southgate had recently been an international player, he had no opportunity to undertake the coaching courses. He did go on to complete his coaching qualifications.

In his first season in charge, Southgate guided Middlesbrough to 12th position in the Premier League. His biggest win as a manager was an 8–1 victory against Manchester City in May 2008. In December 2007, Arsenal manager Arsène Wenger suggested Southgate as one of several English managers who were “all good enough” to manage the national team. He faced some criticism early in the 2007–08 season after Boro had a spell in the relegation zone, but they later pulled clear of the bottom three.

In November 2008, Southgate took Middlesbrough up to 8th place after an away win against on-form Aston Villa; however, Boro would thereafter go 14 games without a win, finally defeating Liverpool at home 2–0 on 28 February 2009. After an away defeat against Stoke City, some of the travelling supporters were calling for his dismissal after only achieving one win in 18 games and relegation survival looking unlikely. On 24 March, chairman Steve Gibson announced that sacking Southgate would not “help the situation”. Middlesbrough finished in 19th position and were relegated to the Championship after a 2–1 defeat at West Ham United. Southgate said he was determined to get the club back into the Premier League, praised the supporters and said that he felt for them.

On 20 October 2009, shortly after a 2–0 victory over Derby County, Southgate was dismissed as manager with Middlesbrough in fourth place in the Championship. The dismissal was controversial as he had taken Boro to within one point of the top position, but Gibson said he had made the decision weeks earlier in the best interests of the club.

Southgate was also a co-commentator for ITV at the 2006 World Cup, covering group games alongside Clive Tyldesley. His appointment as Middlesbrough manager two days before the start of the tournament meant that he left Germany before the knockout phase began, with David Pleat replacing him as Tyldesley’s co-commentator. He resumed a role as pundit and co-commentator after he finished his tenure at Middlesbrough in 2010, working on FA Cup and UEFA Champions League matches for ITV as well as acting as a pundit on England games.

In January 2011, Southgate was appointed as the FA’s head of elite development, to work with Sir Trevor Brooking. He left the post in July 2012, and ruled himself out of consideration for the role of technical director, for which he had been a leading candidate.

In August 2013, Southgate was named manager of the England under-21 team, signing a three-year contract. In his first game in charge, they beat Moldova 1–0 in a European Championships qualifier thanks to a goal from Saido Berahino. Under Southgate England qualified for the finals of the European Under-21 Championship in 2015, where they were knocked out in the group stages, finishing last in their group.

Southgate was put in temporary charge of the senior England team on 27 September 2016, when Sam Allardyce resigned after one game due to the 2016 English football scandal. England were in the early stages of qualifying for the 2018 FIFA World Cup. After winning his first game in charge 2–0 against Malta, under Southgate’s leadership, England went on to draw 0–0 with Slovenia, beat Scotland 3–0, and in his last game in temporary charge, drew 2–2 with Spain, despite leading 2–0 and conceding goals in the 89th and 96th minutes. Southgate’s spell as caretaker manager ended on 15 November.

On 30 November 2016, Southgate was appointed as England manager on a four-year contract.

The England team qualified for the 2018 FIFA World Cup on 5 October 2017, with a 1–0 home win over Slovenia. The Football Association confirmed in December that Southgate would remain as England manager even if the team did not progress beyond the group stage of the tournament, describing their expectations as “realistic” and the tournament as “a really important staging post for our development”.

After wins against Tunisia and Panama saw England qualify behind Belgium in their World Cup group, Southgate’s England side beat Colombia 4–3 on penalties in the round of 16 after a 1–1 draw on 3 July 2018 to claim his nation’s first ever World Cup penalty shoot-out victory and a place in the quarter-finals. On 7 July 2018, Southgate’s England side beat Sweden 2–0 in the quarter-finals, with Southgate becoming the first England manager to reach the semi-finals of the World Cup since Sir Bobby Robson in 1990. This success bought Southgate significant admiration from England fans. For the semi-final with Croatia, fans dressed up in Waistcoats in tribute to Southgate’s iconic waistcoat, which he wore during England’s matches: retailer Marks & Spencer reported a 35% increase in sales of waistcoats, and the hashtag ‘WaistcoatWednesday’ trended on Twitter. A week after the end of the tournament, Southgate tube station in Enfield, London, was renamed to “Gareth Southgate” for two days in recognition of Southgate’s achievement. Southgate was also lauded for personal qualities shown in the World Cup, including consoling Mateus Uribe, a Colombian player, whose missed penalty had seen England win.

On 11 July 2018, Southgate’s England side suffered a 2–1 defeat to Croatia during extra time in the semi-finals. Kieran Trippier opened the scoring for England with a free kick, before a goal from Ivan Perišić sent the tie into extra time. Mario Mandžukić scored the winner for Croatia in the second half of extra time. With England trailing, the match also saw England play the final ten minutes of extra time with ten men as Trippier suffered an injury after Southgate had already made his permitted substitutions. Following a 2–0 defeat to Belgium in the third place play-off, England ended the World Cup in fourth place. Harry Kane, a striker and the England team captain, also won the Golden Boot as the tournament’s top goal-scorer.

In 2019, Southgate managed England to third place in the inaugural UEFA Nations League. They did so after finishing top of a group containing Spain and Croatia. Their 3–2 victory away against the Spanish was their first victory in Spain for 31 years. They lost 3–1 to the Netherlands in the semi-final but then beat Switzerland 6–5 in a penalty shootout after the match finished goalless. It was England’s first third-place finish in a major international tournament since UEFA Euro 1968.

Southgate was appointed an Officer of the Order of the British Empire (OBE) in the 2019 New Year Honours for services to football. In April 2020 during the COVID-19 pandemic, Southgate agreed to take a 30% cut in his salary.