John Laurens Manning Irby (September 10, 1854 – December 9, 1900) was a United States senator from South Carolina.

He studied law, was admitted to the bar in 1875, commenced practice at Cheraw, and returned to Laurens.

He was appointed lieutenant colonel of the South Carolina Militia in 1877 and that year was also intendant of Lauren.

While in the Senate, he was chairman of the Committee on Transportation Routes to the Seaboard (Fifty-third Congress).

He resumed the practice of law and also engaged in agricultural pursuits; he died in Laurens in 1900; interment was in the City Cemetery.