Abraham H. Foxman, a Holocaust survivor who became the nation's most prominent voice against antisemitism as national director of the Anti-Defamation League for nearly three decades, died Sunday in Manhattan at 86. Born Avraham Chanoch Hanach Fuksman in 1940 in what is now Belarus, he spent four years hidden with a Christian nanny who had him baptized as Catholic while his parents fled Nazi occupation.

From 1987 to 2015, Mr. Foxman led the ADL, building it into an organization with a $60 million budget and 27 offices across the United States and Jerusalem. He met regularly with presidents, prime ministers and Pope John Paul II, becoming the go-to voice for comments on every antisemitic incident—from synagogue firebombings to celebrity bigoted remarks. His 2003 book, "Never Again?: The Threat of the New Anti-Semitism," criticized European leaders for failing to address rising anti-Jewish violence.

A 2014 ADL survey of 102 countries found one in four respondents believed classic antisemitic stereotypes about Jewish control of finance and media, while half of 53,100 adults surveyed had never heard of the Holocaust. Mr. Foxman famously accepted apologies from figures like John Galliano and Mel Gibson—if they agreed to study Jewish history or visit Auschwitz. He retired in 2015, having transformed the ADL into a broader civil rights organization while keeping antisemitism his central mission.