Magnolia grandiflora, commonly known as the southern magnolia or bull bay, is a tree of the family Magnoliaceae native to the southeastern United States, from southeastern North Carolina to centralFlorida, and west to East Texas.

Although endemic to the lowland subtropical forests on the Gulf and south Atlantic coastal plain, magnolia grandiflora is widely cultivated in warmer areas around the world. The timber is hard and heavy, and has been used commercially to make furniture, pallets, and veneer.

M. grandiflora contains phenolic constituents shown to possess significant antimicrobial activity. Magnolol, honokiol, and 3,5-diallyl-2′-hydroxy-4-methoxybiphenyl exhibited significant activity against Gram-positive and acid-fast bacteria and fungi. The leaves contain coumarins and sesquiterpene lactones.