Benjamin "Ben" Weider, (February 1, 1923 – October 17, 2008) was the co-founder of the International Federation of BodyBuilding & Fitness (IFBB) along with brother Joe Weider. He was a Canadian businessman from Montreal, well known in two areas: Bodybuilding and Napoleonic history.

Benjamin Weider was born on February 1, 1923 in Montréal, Québec, Canada, to Louis and Anna Weider, Polish Jewish emigrants from the town of Kurów in Poland.

In bodybuilding he founded and ran a physical fitness and sporting goods company bearing his name. 

He was President of The International Federation of Bodybuilding Fitness a.k.a. IFBB until October 29, 2006, when he announced his retirement.

Created in 1998 under direct supervision of IFBB Founder and Honorary Life President Mr. Ben Weider, ifbb.com provides to millions of bodybuilders fitness athletes, officials, supporters and fans, from all over the world (our statistics have recorded visits from 187 countries) accurate information on events, news, rules, history and, in general, all the activities carried on by IFBB and the affiliated continental and national federations; that build together in a daily basis, the reality of our sport with over a thousand events organized each year, under IFBB logo, in the five continents.

The IFBB affiliates National Federations from 199 countries and is a member of the SportAccord (former General Association of International Sports Federations – GAISF) and the International World Games Association (IWGA); it is recognized by the Olympic Council of Asia (OCA) and over 90 National Olympic Committees (NOCs); as well as being a member of the World Anti-Doping Agency, that has recognized the IFBB as the only authority in bodybuilding, whose anti-doping program is in full compliance with the WADA Code.

In Napoleonic circles, Weider was known as a forceful advocate of the theory that Napoleon was assassinated by a member of his entourage during his exile in Saint Helena. He co-authored several books, Assassination at St. Helena and Assassination at St. Helena Revisited, with Sten Forshufvud and The Murder Of Napoleon, with David Hapgood about this. Weider also founded the International Napoleonic Society, of which he was the President, and wrote numerous articles for this organization.

In 1975 he was made a Member of the Order of Canada and was promoted to Officer in 2006. In 2000, he was made a Knight of the National Order of Quebec. On October 12, 2000, he received the French Legion of Honor, that country's highest honour, which was established by Bonaparte himself. Weider was also a 1984 nominee for the Nobel Peace Prize, a member of the Quebec Sports Hall of Fame, and a Commander of the Venerable Order of St. John. He also had several honorary doctorate degrees. The Institute on Napoleon and the French Revolution at the Florida State University History Department has recently created the Ben Weider Chair in Revolutionary Studies. In total, Ben accumulated over 66 awards and honours during his lifetime.

From 1998 to 2005, Ben Weider was Honorary Lieutenant Colonel of the 62nd (Shawinigan) Field Artillery Regiment, RCA. In 2005, he was promoted to Honorary Colonel of that military unit. In October 2006, Ben Weider unexpectedly retired as president of the IFBB.

In 2008, he was given the Lifetime Achievement Award at the 20th Anniversary Arnold Classic (only the eighth time in the competition's history that this award had been presented).

Weider owned one of the most extensive collections of Napoleon memorabilia, including one of the bicorne hats worn by Napoleon during the invasion of Russia in 1812, of which only 12 are known to still exist today. Three weeks before his death, he donated his entire set of Napoleonic artifacts, over 60 pieces in all, to the Montreal Museum of Fine Arts, making it one of the largest collections of its kind in the world. Prince Charles Napoleon, great-great-grandson of Napoleon's youngest brother Jerome, was on hand to inaugurate the museum's new permanent gallery on Oct. 23, 2008.

The Ben Weider foundation has donated gyms around the world as part of their bodybuilding outreach, including in Israel. Ben endowed what is now known as the “Ben Weider Jewish Community Center in Montreal” and also supported two Lubavitch institutions, that are Orthodox Judaism. He was an admirer of Lubavitch head Rabbi Menachem Schneerson, a religious leader who was a major force in Israel; Israeli leaders – including Menachem Begin, Yitzhak Rabin, and Benjamin Netanyahu – would often visit him when they were in the U.S. and seek his advice. 

There is also a Joe Weider Foundation; Joe Weider is CEO and Eric Weider has been CFO and is currently President. This has given several large grants to a Los Angeles-based organization called American Friends Of Aish HaTorah. Aish HaTorah is an Israeli organization that opposes Jewish assimilation and promotes Israel in the United States. Joe Weider is one of six North American chairmen of The Jerusalem Fund of Aish HaTorah. This focuses on bringing political leaders, corporate executives, investors, and entertainment personages on private trips to Israel to increase their support for Israel.

These foundations also focus their efforts and resources on Jewish based causes in the USA and Israel.

Ben Weider passed away on October 17, 2008, at the Jewish General Hospital in Montreal.

A movie called Bigger was released in 2018 on the life of Ben Weider and his brother Joe Weider. Tyler Hoechlin played Joe Weider, while Julianne Hough plays Betty Weider, his wife, Aneurin Barnard acted in the role of Ben Weider and Calum Von Moger portrayed Arnold Schwarzenegger.