The Dagstuhl Seminar 23191 entitled "Universals of Linguistic Idiosyncrasy in Multilingual Computational Linguistics" took place May 7-12, 2023. Its main objectives were to deepen the understanding of language universals and linguistic idiosyncrasy, to harness idiosyncrasy in treebanking frameworks in computationally tractable ways, and to promote a higher degree of convergence in universalism-driven initiatives to natural language morphology, syntax and semantics. Most of the seminar was devoted to working group discussions, covering topics such as: representations below and beyond word boundaries; annotation of particular kinds of constructions; semantic representations, in particular for multiword expressions; finding idiosyncrasy in corpora; large language models; and methodological issues, community interactions and cross-community initiatives. Thanks to the collaboration of linguistic typologists, NLP experts and experts in different annotation frameworks, significant progress was made towards the theoretical, practical and networking objectives of the seminar.