Benjamin Barr Lindsey (November 25, 1869 – March 26, 1943) was an American judge and social reformer based in Denver during the Progressive Era.

[1] Among other measures to which Lindsey contributed his influence were a reform of the registration law, greatly reducing election frauds; a reform of the ballot; state provisions for the support of the dependents of people serving in prison; extension of the probation system for prisoners; organization of public baths and playgrounds in Denver; the institution of the fresh-air movement in Denver; and enactment of statewide Mother's Pension Law.

He carried on an active propaganda for the general adoption of the juvenile court plan, and for political and social reform, through lectures delivered in many American and foreign cities and through the publication of books and pamphlets, of which The Beast (with Harvey J. O'Higgins, 1910) was widely circulated.

[1] Since one of the most common discourses in the popular culture was about women having children, and many clergy believed that sexual intercourse within marriage should only be for purposes of procreation, Lindsey's essay aroused strong emotions; a number of priests and ministers, as well as civic leaders accused him of promoting immorality, promiscuity and free love, charges that he denied.

[3] Bertrand Russell, in his 1929 book Marriage and Morals, wrote approvingly of Lindsey's proposals but observed that they "were received with a howl of horror by all middle-aged persons and most of the newspapers throughout the length and breadth of America.

[6] In 1919, Lindsey wrote the introduction to Madeleine: An Autobiography, the memoirs of former prostitute Madeline Blair, an exposé of brothels in the 19th-century American West.

[8] On December 7, 1930, he was arrested for disorderly conduct after disrupting public worship at the Cathedral of St. John the Divine in New York City.