Thomas D. O'Brien

Thomas Dillon O'Brien (February 14, 1859 – September 3, 1935) was an American lawyer, judge, and academic from Minnesota.

He was one of the five co-founders of William Mitchell College of Law and a justice of the Minnesota Supreme Court.

O'Brien was born in the Wisconsin town of La Pointe, on Madeline Island on February 14, 1859.

In 1891, he sought and won election as Ramsey County Attorney, although he only served for one term.

In September 1909, Governor John Albert Johnson appointed him to be an associate justice of the Minnesota Supreme Court.