John B. Moran (April 27, 1859 – February 6, 1909) was an American politician who served as District Attorney of Suffolk County, Massachusetts, from 1905 to 1909.

[2] He opened a small law office in Woburn, Massachusetts, but moved to Roxbury after six months due to slow business.

During the 1892 election he took the stump for Timothy V. Coakley, Democratic nominee in the Massachusetts Senate's 8th Suffolk District.

[5][6] In 1898, Moran severely criticized Suffolk County District Attorney Oliver Stevens, who was running for reelection.

Moran accused Stevens and his assistants of making decisions based on political influence, requesting unjust sentences, shielding perjurers, and other misdeeds.

Moran ran on a platform opposing graft and, following the death of Susie Geary, vowed to close down abortion clinics.

[10] Soon after taking office, Moran closed an investigation into alleged plot to kill Martin Lomasney due to a lack of evidence.

[18] By September 26, Moran had such a large lead in Democratic delegate count that leaders of conservative wing of the party decided that they would not present their candidate, Henry Melville Whitney, at the convention.

[22] On October 18, Moran announced that if he was elected and reelected in 1907, he would challenged both Bryan and Hearst at the 1908 Democratic National Convention.

His physician informed him that an active campaign, along with working full-time as District Attorney, would result in permanent injury to his already frail condition.

[27] Following his defeat in the gubernatorial election, Moran considered running for Governor, Mayor of Boston, or District Attorney in 1907.