| J. Mercer Johnson | |
| Office6: | Justice of the Arizona Supreme Court |
| Term Start6: | September 16, 1957 |
| Term End6: | September 20, 1960 |
| Predecessor6: | Arthur T. LaPrade |
| Successor6: | Robert O. Lesher |
| Birth Date: | 20 October 1906 |
| Birth Place: | Naco, Arizona Territory, U.S. |
| Death Place: | Tucson, Arizona, U.S. |
| Party: | Democrat |
John Mercer Johnson[1] (October 20, 1906 – December 17, 1988) was a justice of the Supreme Court of Arizona from September 16, 1957 to September 20, 1960.[2]
Born in Naco, Arizona Territory, Johnson ran for Pima County Attorney in 1936, losing in the primary election. Two years later, he became the Democratic nominee and won the position. He was reelected three times. Johnson became a Superior Court judge in 1946. He served in that position until becoming an Arizona Supreme Court Justice in 1957, appointed by Governor Ernest W. McFarland to fill the vacancy caused by the death of the late Justice Arthur T. LaPrade. He stepped down from the Court in 1960 to return to private practice.[3] Johnson became a partner at the firm Johnson, Dowdall & Terry in Tucson. There, Johnson represented Conoco.[4] [5] He died on December 17, 1988.[6]