Low-Mass X-ray Binaries

A large fraction of X-ray sources in our Galaxy are low-mass X-ray binaries, containing a black hole or a neutron star accreting from a gravitationally bound low-mass ($\le$1 M${}_{\odot }$) companion star. These systems are among the older population of stars and accreting systems in the Galaxy, and typically have long accretion histories. Low-mass X-ray binaries are categorized into various sub-classes based on their observed properties such as X-ray variability and brightness, nature of the companion star and/or the compact object, and binary configuration. In this Chapter, we review the phenomenology of sub-classes of these systems and summarize observational finding regarding their characteristics, populations, and their distribution in the Galaxy.