Moishe Rosen, 78, a flamboyant and controversial convert to Christianity who founded the missionary group Jews for Jesus, died Wednesday in San Francisco.
The cause was prostate cancer, the group announced.
Mr. Rosen launched Jews for Jesus in San Francisco in 1973 and over the next decade turned it into a flourishing movement that drew thousands of converts from among the youthful seekers of the counterculture era. Its success stirred the wrath of Jewish leaders, who denounced him as a cultist and fought back through groups such as Jews for Judaism.
Evangelical leaders praised his dynamism while noting his provocative style.
Mr. Rosen saw himself as a hybrid who did not regard a Jew who believed in Jesus as a contradiction.
"I never made the decision that I wanted to leave the Jewish community," he told New York magazine in 1986. "We want to stay in and dissent - and we've been ostracized. We wouldn't separate the two religions. We want a climate where all ideas can be accepted or rejected without previous indoctrination."
By the time he retired as executive director in 1996, Jews for Jesus had grown into a sophisticated organization with a $13 million budget and seven overseas branches.
Mainstream Jewish leaders never let up on their criticism, arguing that a Jew for Jesus was as impossible as kosher pork. But Mr. Rosen continued to insist otherwise.