This chapter defines thermodynamic and kinetic water stability for metal–organic frameworks (MOFs) and discusses how these properties are determined. Water adsorption isotherms are presented for several different MOF materials to illustrate that variations in the organic group of the MOF can produce changes in the water adsorption behavior. Water adsorption in stable rigid MOFs is shown to be consistent with the water adsorption behavior of traditional adsorbents, such as carbons and zeolites. A list of various MOFs is presented, and the materials are classified using kinetic and thermodynamic stability definitions. Lastly, strategies for improving MOF stability are discussed.