LuEsther T. Mertz Library, The New York Botanical Garden, Research library at New York Botanical Garden, The Bronx, United States

The LuEsther T. Mertz Library is a four-story Renaissance Revival building at the New York Botanical Garden in the Bronx, designed by Robert W. Gibson and completed in 1901. Its facade is gray-buff brick with buff terracotta, and the Fountain of Life and the Tulip Tree Allee stand outside the front entrance. It holds scholarly books and serials on botany and horticulture, plus rare works used in history, anthropology, landscape design, and environmental policy.

The library was founded in 1899 with an initial collection of 2,500 volumes, immediately strengthened by the addition of 5,000 books from Columbia College's botanical collection. This foundation allowed it to develop into one of the most important centers for botanical research.

The library's name honours LuEsther Mertz, who funded its 1990s renovation; it was founded in 1899 and renamed for her. Its reading rooms serve studies ranging from ethnobotany and economic botany to landscape and architectural history, urban social history and environmental policy. Outside the entrance runs the Tulip Tree Allee, a tree-lined avenue.

The library sits near the garden's main entrance at Southern Boulevard and Bedford Park Boulevard, about 1,000 feet (300 m) east of the Botanical Garden Metro-North station. The Fountain of Life and the Tulip Tree Allee stand outside the front entrance, so the approach on foot passes both. The building is a four-story walk-up with a front staircase and balustrade.

The Fountain of Life outside the entrance was built by Wilson & Baillie Manufacturing under an April 1901 contract, which also covered the front approaches and cornice ornamentation. The fountain, the Tulip Tree Allee and the building were all listed as contributing resources when the garden became a National Historic Landmark in 1967, and all three were designated New York City landmarks in 2009.