Manchester United forward Marcus Rashford said he received “at least 70 racial slurs” on social media following Wednesday’s Europa League final loss to Villarreal.
United later tweeted to say their players had been subjected to “disgraceful racist abuse”.
United side lost 11-10 on penalties after a 1-1 draw in Gdansk, Poland.
“At least 70 racial slurs on my social accounts counted so far,” Rashford wrote on Twitter.
“For those working to make me feel any worse than I already do, good luck trying.”
The Department for Education is looking into the matter in relation to the allegation a teacher was behind some of the racial abuse.
In another tweet, Rashford said he was “more outraged” that one of the abusers who sent him a direct message appeared to be a maths teacher, adding: “He teaches children. And knows that he can freely racially abuse without consequence.”
It is understood the account has been deleted and the abuse will be reported to police by the club.
A United spokesperson said: “Everyone at Manchester United is disgusted by the online hate and abuse aimed at Marcus and other players on social media.
“There is simply no excuse for it and we utterly condemn it.
“Manchester United has zero tolerance of any form of racism or discrimination and we encourage people to report it through manutd.com.
“We also urge social media platforms and regulatory authorities to strengthen measures to prevent this disgusting behaviour.”
Facebook, which owns Instagram, called the abuse “abhorrent”.
“We swiftly removed a number of comments and accounts for breaking our rules,” a company spokesperson said.
“We’re currently rolling out a new tool which, when turned on, will help prevent anyone seeing messages like this again. No single thing will fix this challenge overnight but we’re committed to doing what we can to keep our community safe from abuse.”
In April Instagram announced a tool to enable users to automatically filter out abusive messages from those they do not follow.
England forward Rashford has spoken previously about racist abuse he has received.
In January, he said he was subjected to “humanity and social media at its worst” following a 0-0 draw with Arsenal.
A number of players in English football, including several of Rashford’s United team-mates, have been targeted by online discrimination in recent months.
A number of clubs, players, athletes and sporting bodies took part in a four-day boycott of social media in April to encourage companies to take a stronger stance against racist and sexist abuse.
This month United said it found a 350% increase in abuse directed towards their players, with 3,300 posts targeting them between September 2019 and February 2021.
The club set up an online reporting system, encouraging fans to flag up online abuse.