FLAC, Fast Lagrangian Analysis of Continua, is numerical modeling software for advanced geotechnical analysis of soil, rock, groundwater, and ground support in both two- and three-dimensions. FLAC is used for analysis, testing, and design by geotechnical, civil, and mining engineers. It is designed to accommodate any kind of geotechnical engineering project that requires continuum analysis.

The software was first developed in 1986 by Itasca Consulting Group, Inc. Itasca was founded by faculty members of the Department of Civil and Mineral Engineering at the University of Minnesota to provide services in rock mechanics, numerical modeling of geotechnical environments, and underground space use.