John M. Greaney (born 1939) is a former Associate Justice on the Supreme Judicial Court of Massachusetts and director of the Macaronis Institute for Trial and Appellate Advocacy at Suffolk University Law School.
John Greaney was born in Westfield, Massachusetts on April 8, 1939 and graduated from St Mary's High School and from the College of the Holy Cross and New York University School of Law. Greaney served in the Massachusetts National Guard and practiced law for about 10 years before becoming a judge. In 1974, he became a judge on Hampden County Housing Court and in 1976, a Justice of the Massachusetts Appeals Court. Greaney was appointed to the Supreme Judicial Court on September 9, 1989 and wrote a famous concurrence in Goodridge v. Department of Public Health. In 2008 Justice Greaney retired from the court and was appointed director of the Macaronis Institute for Trial and Appellate Advocacy at Suffolk University Law School in Boston.