The 2023 INFORMS GDN Appreciation for Outstanding Service Award is conferred on Rudolf Vetschera for his exceptional service contributions to the INFORMS Group Decision and Negotiation (GDN) Section. He was President of the GDN Section from 2019 to 2021, during the difficult years of the COVID-19 pandemic. Before that, he served two years each as Vice President (VP) for Meetings and VP for Membership and Publications. He was involved in the organization of many GDN conferences, serving as organizer of the conference in Vienna in 2005, Chair of the Doctoral Consortium in 2013, 2015 and 2023, Program Chair in 2016 and 2017, General Chair in 2017, 2019, 2020 and 2021, and Editor of the conference proceedings in 2016, 2018, and 2019. He has also served the GDN Section in many other ways, as member of the board, participant in award committees and similar functions. Since 2014, he has been Departmental Editor of the GDN journal for the area "Artificial Intelligence and Management Science." He has edited two special issues for the GDN journal, as well as special issues on topics related to GDN in other journals.