John Gregg may refer to:

• John Gregg (archbishop of Armagh) (1873-1961) Anglican Archbishop of Armagh 1939-59
• John Gregg (baker) (d.1964), founder of Greggs bakery
• John Gregg (bishop of Cork) (d.1878), Anglican Bishop of Cork, Cloyne and Ross, 1862-78
• John Gregg (CSA) (1828-64), Confederate general
• John Gregg (UDA) (1957?-2003), Ulster loyalist
• John Irvin Gregg (1826-92), Union general
• John P. Gregg, head football coach at Louisiana State University, 1899
• John R. Gregg, Indiana state representative 1986-2002
• John Robert Gregg (1867-1948), inventor of Gregg shorthand
• John William Gregg (d.1969) landscape architect

[ Source: Wikipedia ]