We construct a Continuous Wavelet Transform (CWT) on the torus T 2 following a group-theoretical approach based on the conformal group SO(2, 2). The Euclidean limit reproduces wavelets on the plane R 2 with two dilations, which can be defined through the natural tensor product representation of usual wavelets on R. Restricting ourselves to a single dilation imposes severe conditions for the mother wavelet that can be overcome by adding extra modular group SL(2, Z) transformations, thus leading to the concept of modular wavelets. We define modular-admissible functions and prove frame conditions. MSC: 81R30, 81R05, 42B05, 42C15