Zachary is a city in East Baton Rouge Parish, Louisiana, United States. It lies 16 miles (26 km) north of the city of Baton Rouge, and had a population of 14,960 at the 2010 census, up from 11,275 in 2000. At the 2020 census, Zachary’s population increased to 19,316.

Much of the home which the city now occupies was share of a 160-acre (65 ha) farm owned by Darel Zachary (1827-1907). In the 1880s, Zachary sold his estate to the Illinois Central Railroad, who built a track and a depot on it. A village quickly grew up not far away off from the depot, which came to be called “Zachary” after the native farmer. Zachary’s first declare office was opened in 1885, and it was incorporated as a city upon August 2, 1889, with Thomas Edward McHugh as its first mayor. A blaze devastated the city in 1903, supposedly caused by a greengrocer bothersome to flame-ripen his bananas. The “historic village” at the center of the city is composed of buildings which either survived the fire, or were built rudely after it, the oldest (excluding the depot) being the 1898 Allison House. The first census was carried out in 1914 and reported just 419 residents. In 1966 Zachary became the first city in Louisiana previously the Reconstruction Era to elect a Republican as mayor, Jack Louis Breaux.

Zachary is located in northern East Baton Rouge Parish. It is bordered to the north by the city of Slaughter, to the east by Central, and to the south by Baker. Louisiana Highway 19 passes through the city, leading north 5 miles (8 km) to the middle of Slaughter and south 9 miles (14 km) to U.S. Route 61 in the northern share of Baton Rouge.

According to the United States Census Bureau, Zachary has a total Place of 24.0 square miles (62.1 km), of which 23.9 square miles (62.0 km²) is land and 0.04 square miles (0.1 km), or 0.13%, is water.