The OpenSourceMANO community organised the OSM#16 Ecosystem Day on Wednesday, 29th November 2023. The event was run remotely during the OSM#16 Plenary Meeting taking place 28th November to 1st December 2023. The OSM Ecosystem Day allows organizations in the OSM Ecosystem to share about their Open Source MANO experience and how OSM is helping them to achieve their goals. Presentations and demos cover a wide range of aspects from research activities in academia to production deployments and commercial initiatives, mostly focusing on cutting-edge Telco use cases.