[en] The production of K_S⁰ mesons is studied using deep-inelastic scattering events (DIS) recorded with the H1 detector at the HERA ep collider. The measurements are performed in the phase space defined by the four-momentum transfer squared of the photon, 145 GeV² < Q². The differential production cross sections of the K_S⁰ meson are presented as function of the kinematic variables Q² and x, the transverse momentum p_T and the pseudorapidity η of the particle in laboratory frame, and as function of the momentum fraction x_p^BF and transverse momentum p_T^BF in the Breit Frame. Moreover, the K_S⁰ production rate is compared to the production of charged particles and to the production of DIS events in the same region of phase space. The data are compared to theoretical predictions, based on leading order Monte Carlo programs with matched parton showers. The Monte Carlo models are also used for studies of the flavour contribution to the K_S⁰ production and parton density function dependence. (orig.)