Chelsea have adopted the International Holocaust Remembrance Alliance's (IHRA) definition of anti-Semitism and the organisation's executive secretary hopes other football clubs follow suit.
The decision comes as part of Chelsea's "Say No to anti-Semitism" campaign, which was launched in January 2018, and follows the official presentation of a commemorative mural of Jewish footballers and British prisoners of war on a wall outside Stamford Bridge's West Stand on Wednesday.
The IHRA definition is: "Anti-Semitism is a certain perception of Jews, which may be expressed as hatred toward Jews. Rhetorical and physical manifestations of antisemitism are directed toward Jewish or non-Jewish individuals and/or their property, toward Jewish community institutions and religious facilities."
Chelsea accused a section of their fans of anti-Semitic chanting during a Europa League game at Vidi in December 2018, although the club received no punishment from UEFA.
IHRA executive secretary Kathrin Meyer praised the club's work on discrimination against Jews and hopes they prove to be trailblazers in football.
"This definition is a tool to raise awareness and be informed to fight anti-Semitism," said Meyer at a news conference at Chelsea's Cobham training ground.
"It couldn't be more urgent. Anti-Semitism kills people, not just in football, and attacks our societies. The step Chelsea are taking with this and the 'Say No to anti-Semitism' campaign is huge.
"I hope other clubs follow, it needs to be a bottom-up effort. We wish Chelsea all the best of luck with their endeavours."
Chelsea chairman Bruce Buck said: "All our players have been involved in our efforts. This week we unveiled a mural on the West Stand at Stamford Bridge.
"Adopting this definition is a big moment for this club. It brings clarity to the whole subject of what is anti-Semitic. Everyone will be fully aware of the definition. It's been adopted by around 35 countries and British Police.
"We know it's a long battle … this is a problem that has existed for a long time, the Holocaust is something we have to make sure never happens again. We all have to work at this.
"In 2017 there were a number of anti-Semitic incidents around the world. It came around, and we wanted to do something about it."
Chelsea head coach Frank Lampard added: "I think it's an important statement, we hope it makes an impact, that's the whole point.
"In simple terms as manager of the football club, I am proud that the club takes such a strong stance against any form of discrimination and we'll be active in that going forward, which I think today shows.
"Words are one thing but actions are another, and we'll always be very strong on that and will continue to be so."