The move came after Manchester-born Rashford, who made 426 senior appearances and scored 138 goals for United in all competitions, fell out of favour with manager Ruben Amorim.
Barcelona stay on course to defend their Copa del Rey title with a 2-1 win over Albacete.
Manchester United's exiled forward Marcus Rashford has delivered a scathing assessment of the Premier League side's struggles
Rashford, one of Europe's top talents before falling out of favour at United and spending the latter part of last season on loan at Aston Villa, joins a stellar attacking cast featuring Robert Lewandowski, Raphinha, Dani Olmo and Ferran Torres.
Rashford is not my player at the moment but every player that performs well on loan is good news for my club.
Barcelona outclassed Mallorca 3-0 at home on Saturday to increase their lead at the top of the LaLiga standings.
Aston Villa striker Marcus Rashford scored twice in a 3-0 defeat of second-tier Preston North End in their FA Cup quarter-final at Deepdale on Sunday to earn a Wembley semi-final against fellow Premier League team Crystal Palace.
Despite Rashford's omission, Amorim assured that the rest of the team remains unaffected by the decision.
Harry Kane scored his 36th goal of the season but Bayern Munich let a second-half lead slip to draw 2-2 with Hamburg SV.
Stuttgart stumble to 1-1 against Union, miss out on top three
Rashford absence an 'internal matter', says Ten Hag
IMAGES from the UEFA Champions League matches played on Wednesday.
The 21-year-old Alejandro Garnacho's sale value is the fourth largest for a United player after Cristiano Ronaldo, Romelu Lukaku and Angel di Maria.
Christensen, Rashford on target as Barcelona beat Guadalajara in Copa del Rey
England begin their World Cup group campaign against Iran on November 21.
Sevilla ended defending champions Barcelona's unbeaten streak in the Spanish League with a crushing 4-1 defeat, in Madrid, on Sunday.
On debut, substitute Marcus Rashford became the first Englishman to play a first-team game for Barcelona since former England striker Gary Lineker in 1989.
The result keeps Barcelona second in the table on 16 points from six games, two behind leaders Real Madrid. Oviedo remain 18th with just three points.
While England boast a formidable attacking threat, there are concerns about their defence which is perhaps why Southgate is prepared to look at new candidates before he has to make his final call for the tournament.
Man United get injury boost ahead of Liverpool FA Cup clash
Rashford earned praise during the COVID-19 pandemic when he launched a child food poverty campaign, which prompted a government U-turn in 2020.
Barcelona staged a thrilling second-half comeback to defeat Levante 3-2 away in LaLiga on Saturday, overcoming a two-goal deficit after a poor first-half display.
'I overslept a bit. It can happen.'
Raphinha struck twice late in the second half as Barcelona secured a hard-fought 2-0 victory over a resolute Osasuna side on Saturday, extending their lead at the top of the LaLiga standings to seven points.
After successfully dismissing Afghanistan's Ibrahim Zadran, Bumrah was seen emulating the way Manchester United footballer Marcus Rashford celebrates a goal.
Erik ten Hag's side, featuring several players who played in the World Cup in Qatar, could have doubled their lead when Anthony Martial's shot was well saved by Burnley goalkeeper Bailey Peacock-Farrell.
Barcelona closed the gap on their rivals Real Madrid, moving up to 28 points and pulling two clear of third-placed Villarreal.
IMAGES from UEFA Champions League matches played on Wednesday
Rashford said he spoke to Prime Minister Boris Johnson on Saturday and was briefed about the government's plans to provide 170 million pounds ($220 million) of extra funding to the campaign.
'You have stood up for us repeatedly, now it's time for us to stand up for you!'
Parliament on Wednesday rejected a Labour Party motion to extend free school meals until Easter 2021 from the cut-off before the half-term and winter holidays, prompting the England international to launch his campaign on social media.
Araujo to miss Uruguay friendlies due to thigh injury
A summary of Wednesday's action in the UEFA Champions League.
IMAGES from the FIFA World Cup Group B match played between Wales and England on Tuesday.
Barcelona stripped Marc-Andre ter Stegen of the captaincy on Thursday as a feud escalated between the Germany goalkeeper and the club over his injury status amid the Catalans' attempts to register new signings.
Liverpool shrugged off the absence of Mohamed Salah as midfielder Dominik Szoboszlai scored an 88th-minute penalty to give them a 1-0 Champions League win at Inter Milan.
Erling Haaland is the tenth player to reach the landmark of 50 goals in the UEFA Champions League and fastest to do so, beating the 62-match record of Ruud van Nistelrooy.
The 22-year-old will follow in the footsteps of Manchester United legends Alex Ferguson and Bobby Charlton by receiving an honorary doctorate, the highest honour the university can bestow.
Southgate called the goal 'world class' but he was just as happy with the all-round play of the 20-year-old Manchester United forward.
Other contenders for the award, voted for by the public in December, include Mercedes Formula One driver Lewis Hamilton and Liverpool skipper Jordan Henderson who are both at 12/1.