Gathering the proceedings of the 6th IFToMM International Conference on Mechanisms, Transmissions, and Applications (MeTrApp), held in Poitiers, France, on May 24-26, 2023, this volume covers topics such as mechanism and machinery design, parallel manipulators, robotics and mechatronics, control applications, mechanical transmissions, cam and gear mechanisms, and dynamics of machinery. MeTrApp 2019 provided researchers, scientists, industry experts, and graduate students from around the globe with a platform to share their cutting-edge work on mechanisms, transmissions, and their applications. The proceedings extend this platform to all researchers, scientists, industry experts, and students interested in these fields.