Iberian Strings 2023 is the 15th-installment of the annual meeting of the Spanish and Portuguese String Theory community, where recent developments in the field of supergravity, strings, branes and gauge theory are discussed. The three day meeting will have 7 one hour invited talks, as well as contributed talks, that center around the latest developments in String Theory, the AdS/CFT correspondence, Quantum Gravity and Quantum Field Theories as well as the profound relations among them. The workshop is structured in a discussion-friendly schedule and located in very friendly surroundings, with the aim of creating the ideal environment for scientific discussion.