This paper presents the results of a laboratory testing program that was designed to investigate the mechanical behaviour of the Tournemire argillite. Eighty rock samples were obtained from boreholes drilled at different angles in the walls and floor of an existing gallery at the Tournemire Underground Research Laboratory (URL), France. The experimental program consists of the measurement of the physical properties of the argillite and its mechanical response to loading during uniaxial tests, triaxial tests with various confining pressures, unconfined and confined cyclic tests, and Brazilian tests. Since the Tournemire argillite is characterized by the presence of closely spaced bedding planes, the rock specimens were loaded in different directions to bedding planes (i.e., loading orientation angle, θ = 0°, 30°, 45°, 60°, and 90°). Acoustic emission data were also recorded to detect the initiation and propagation of micro-cracks during the uniaxial tests. Most of the tests were performed at the natural moisture content of the rock specimens as delivered to CANMET Laboratories in Ottawa, Canada, where the experiments were conducted. The main objective of the testing program is to identify the mechanical properties of the Tournemire argillite. This paper mainly focuses on the description and interpretation of the test results. The development of an elastoplastic-damage model to describe the mechanical behaviour of the Tournemire argillite is the subject of another paper.