This deposit includes the data used for the research presented in 'Validation of SMAP L2 passive-only soil moisture products using in situ measurements collected in Twente, The Netherlands' that will be submitted (d.d. September 5th, 2019) to the open access scientific journal Hydrology and Earth System Sciences (HESS). The data consists of: • In situ soil moisture and temperature measured from January 2015 till December 2018 at a soil depth of 5 cm by a network composed of twenty stations in the Twente region. The network of soil moisture stations is operated by the University of Twente. • Root zone soil moisture simulations for the Netherlands at 250 m resolution performed by the LHM (Landelijk Hydrologisch Model) maintained by Deltares. • NASA SMAP L2 passive-only soil moisture estimates (version R164020) for three reference pixels with different coverages of the Twente network.