The Legacy Survey of Space and Time is an astronomical survey that will map the entire sky visible from Cerro Pachón in Chile during 10 years. The design of the telescope and survey is such that every point in the sky will be imaged hundreds of times in this period with immense applications in galactic and extragalactic astronomy, solar system objects and cosmology. In this talk I will introduce the LSST project, hardware and its scientific goals and CIEMAT's (and Spain's) participation in it.