M.I.A. -- Huge Soccer Team Threatens Lawsuit ... Stop Wearing Our Jersey!

Paris Saint-Germain -- one of the most famous soccer teams in the world -- is going to war with rapper M.I.A. ... claiming she's damaging their reputation by rocking their jersey in a music video.

The whole fight is over M.I.A.'s video for her song, "Borders" -- in which the rapper attempts to shed light on the plight of refugees ... while wearing a Paris Saint-Germain soccer jersey.

The lyrics are critical of people unsympathetic to refugees -- "Guns blow doors to the system. Yeah f*ck 'em when we say we're not with them. We're solid and we don't need to kick them."

In the video -- which features several images of refugees packed in boats -- M.I.A. altered the team's sponsor's slogan "Fly Emirates" to say, "Fly Pirates."

The team had a HUGE issue with the fact M.I.A. used their jersey to make her statement about the international refugee crisis -- claiming the video suggests PSG is part of the problem ... and not the solution.

In fact, PSG honcho Jean-Claude Blanc fired off a letter to M.I.A.'s label saying, "This association is all the more hard to understand that nothing in our activities and in our daily initiatives suggests we have anything to do with the problems highlighted by M.I.A."

Now, PSG is demanding M.I.A. scrub the image of their jersey from her video and says it's considering legal action if she doesn't ... claiming the rapper is damaging the team's "prestigious reputation."

M.I.A. posted the threatening letter on her Twitter page -- but so far, has not issued a formal comment on the situation ... and the video has not been altered.