Philip Hillel Klein, also known as Hillel HaKohen Klein, was a prominent Hungarian-born American Orthodox rabbi who served as the spiritual leader of the First Hungarian Congregation Ohab Zedek for thirty-five years. Renowned as a bridge between traditional European scholarship and the acculturating American Jewish community, he held numerous leadership positions, including the presidency of Agudath Israel of America and the honorary presidency of the Union of Orthodox Rabbis. He was frequently referred to by Hungarian-American Jews as the "Chasam Sofer of America".