Robert Davis Johnson (August 12, 1883 – October 23, 1961) was a U.S. representative from Missouri. Born on a farm near Slater, Missouri, Johnson was educated in the rural graded schools of his native county, and was graduated from the Portland (Indiana) High School in 1901.He attended the Missouri Valley College, Marshall, Missouri.He taught school in Saline Valley and Orearville, Missouri from 1901 to 1907.He served as clerk of the circuit court of Saline County in 1915–1923.While serving as clerk, he also studied law.He was admitted to the bar in 1917 and commenced practice in Marshall, Missouri, in 1923.He served as prosecuting attorney of Saline County in 1925–1928.