Allard K. Lowenstein (born January 16, 1929, Newark, New Jersey, U.S.—died March 14, 1980, New York, New York) was an American scholar, political activist, and diplomat who was known for his unceasing fight against injustice in many forms, evidenced by his participation in such causes as antiapartheid, civil rights, and antiwar protests.
A graduate of Yale Law School (1954), Lowenstein taught at Stanford University, North Carolina State University, and the City College of New York. During the 1960s he participated in a Freedom Ride with a group of college students from the North, riding a bus to Mississippi to support the civil rights of African Americans there. In 1968 Lowenstein scotched U.S. President Lyndon B. Johnson’s hope for reelection by persuading Minnesota Senator Eugene McCarthy to run against him on a "peace" platform opposing the war in Vietnam. Although McCarthy lost the nomination to Vice President Hubert H. Humphrey, his race had been so effective that Johnson finally withdrew his name from nomination.
From 1968 to 1970 Lowenstein served in the U.S. Congress as a Democratic representative from Long Island’s 5th district but failed to win reelection in six other tries. In 1977 he was named a U.S. representative to the UN Commission on Human Rights and later in the year became a U.S. representative on the UN Trusteeship Council. Lowenstein was murdered in his law office by Dennis Sweeney, a mentally ill former student who had worked with him during the civil rights movement.