In this paper we reveal the existence of a large family of new, nontrivial and smooth traveling waves for the 2D Euler equation at an arbitrarily small distance from the Couette flow in H s , with s < 3/2, at the level of the vorticity. The speed of these waves is of order 1 with respect to this distance. This result strongly contrasts with the setting of very high regularity in Gevrey spaces (see [7]), where the problem exhibits an inviscid damping mechanism that leads to relaxation of perturbations back to nearby shear flows. It also complements the fact that there not exist nontrivial traveling waves in the H 3 2 + neighborhoods of Couette flow (see [51]). Contents 1. Introduction and main result 1.1. Sketch of the proof 1.2. Organization 2. Formulation of the problem 2.1. The 2D Euler as an equation for the level curves of the vorticity 2.2. The equation for the traveling wave 2.3. The profile function ε,κ . 3. Bifurcation theory and Crandall-Rabinowitz 4. Functional setting and regularity 4.1. The functional setting 4.2. Hypothesis 1 and 2 5. Analysis of the linear part 5.1. Decomposition of the linear operator 5.2. Rescaling of the decomposition 5.3. One dimensionality of the kernel of the linear operator 5.4. Codimension of the image of the linear operator 5.5. The transversality property 6. Main theorem 6.1. Distance of the traveling wave to the Couette flow 6.2. Full regularity of the solution 7. Appendix References