Argonne National Laboratory is a federally funded research and development center in Lemont, Illinois, United States. Founded in 1946, the laboratory is now sponsored by the United States Department of Energy and administered by UChicago Argonne LLC of the University of Chicago. The facility is the largest national laboratory by size and scope in the Midwest.

Argonne had its beginnings in the Metallurgical Laboratory of the University of Chicago, formed in part to carry out Enrico Fermi's work on nuclear reactors for the Manhattan Project during World War II. After the war, it was designated as the first national laboratory in the United States on July 1, 1946. In the post-war era the lab focused primarily on non-weapon related nuclear physics, designing and building the first power-producing nuclear reactors, helping design the reactors used by the United States' nuclear navy, and a wide variety of similar projects. In 1994, the lab's nuclear mission ended, and although it continues to support many types of nuclear science and technology research, it also maintains a broad portfolio in basic science research, energy storage and renewable energy, environmental sustainability, supercomputing, and national security.

UChicago Argonne, LLC, the operator of the laboratory, "brings together the expertise of the University of Chicago (the sole member of the LLC) with Jacobs Engineering Group Inc." Argonne is a part of the expanding Illinois Technology and Research Corridor. Argonne formerly ran a smaller facility called Argonne National Laboratory-West (or simply Argonne-West) in Idaho next to the Idaho National Engineering and Environmental Laboratory. In 2005, the two Idaho-based laboratories merged to become the Idaho National Laboratory.