Petropoulos, F.Laporte, G.Aktas, E.Alumur, S.Archetti, C.Ayhan, H.Battarra, M.Bennell, J.Bourjolly, J.Boylan, J. E.Breton, M.Canca, D.Charlin, L.Chen, B.Cicek, C.Cox, L.Currie, C. S.M.Demeulemeester, E.Ding, L.Disney, S. M.Ehrgott, M.Eppler, M. J.Erdoğan, G.Fortz, B.Franco, L. A.Frische, J.Greco, S.Gregory, A. J.Hämäläinen, R. P.Herroelen, W.Hewitt, M.Holmström, J.Hooker, J. N.Işık, T.Johnes, J.Kara, B. Y.Karsu, ÖzlemKent, K.Köhler, C.Kunc, M.Kuo, Y.Letchford, A. N.Leung, J.Li, D.Li, H.Lienert, J.Ljubić, I.Lodi, A.Lozano, S.Lurkin, V.Martello, S.McHale, I. G.Midgley, G.Morecroft, J. D.W.Mutha, A.Oğuz, C.Petrovic, S.Pferschy, U.Psaraftis, H. N.Rose, S.2024-03-122024-03-122023-12-270160-5682https://hdl.handle.net/11693/114632Throughout its history, Operational Research has evolved to include methods, models and algorithms that have been applied to a wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first summarises the up-to-date knowledge and provides an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion and used as a point of reference by a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order. The authors dedicate this paper to the 2023 Turkey/Syria earthquake victims. We sincerely hope that advances in OR will play a role towards minimising the pain and suffering caused by this and future catastrophes.en-USCC BY-NC 4.0 DEED (Attribution-NonCommercial 4.0 International)Decision makingEncyclopedia;ModelsOptimisationPracticePrinciplesProgrammingReviewSimulationSystemsTheoryReview10.1080/01605682.2023.22538521476-9360