According to the Associated Press, Fr. Drinan had suffered from pneumonia and congestive heart failure during the previous 10 days.
The Jesuit ran for elected office in 1970, over the objections of his superiors, on an anti-war platform. The priest, who urged the Catholic Church to condemn the Vietnam war as "morally objectionable", was said to consider politics a natural extension of his work in public affairs and human rights.
But his 10 years as a representative of Massachusetts was not without controversy. The priest-politician spoke and voted in favor of access to abortion.
He also opposed the draft and worked to abolish mandatory retirement. He became the first member of Congress to call for the impeachment of Richard Nixon in view of the administration's bombing of Cambodia.
Fr. Drinan left office in 1980, after Pope John Paul II issued a directive barring priests from holding public office.
However, he continued his activism and served as president of Americans for Democratic Action, giving speeches nationwide on hunger, civil liberties, and the arms race. In 1996 Fr. Drinan made waves by speaking in support of President Bill Clinton’s veto of the partial birth abortion ban.
Prior to his political career, Fr. Drinan was the dean of the Boston College Law School from 1956 to 1970. During the 1960s, he called for the desegregation of public schools and urged students to become involved in civil rights.
In the 1990s, the priest testified against the impeachment of Clinton, saying that impeachment should be for an official act, not a private one.
He had received more than 20 honorary degrees in his lifetime.
Fr. Robert Drinan, the only priest ever elected as a voting member of Congress, died peacefully Sunday at Sibley Memorial Hospital in Washington; he was 86.