Abstract 3rd ESS InKind Contribution Diagnostics Forum As part of the In-Kind Contribution (IKC) effort for the ESS project (European Spallation Source), on next April 26-27 Elettra-Sincrotrone Trieste SCpA will organize the 3rd ESS IKC Diagnostics Forum where all the ESS IKC teams, active on the ESS diagnostics development, will meet. During this two day event, which will take place at ICTP Adriatico Guesthouse in Grignano, the advances and the open issues of the differnet ESS diagnostics, currently under development at IKC team laboratories, will be presented and discussed. As typical for this IKC forum series, the scheduled oral sessions are lively interleaved with informal gathering and information exchanges between participants, which definetely make this event a must attend one for the ESS diagnostic IKC community. A total number of 35 to 50 scientists and technicians, joining from the main European laboratories participating to the ESS project, is expected to meet in Trieste. Elettra is one of the three Italian Institutions committed to the realization of the Italian In-kind contribution to ESS, together with INFN and CNR. Besides the contribution to the diagnostics, the other Elettra in kind contributions concern the RF power stations for the spoke cavities, the magnets installed in the linac warm units and in the transfer lines and the power converters for the delivered magnets.