In this paper we prove the convergence of a Crank-Nicolson type Galerkin finite element scheme for the initial value problem associated to the Benjamin-Ono equation. The proof is based on a recent result for a similar discrete scheme for the Korteweg-de Vries equation and utilizes a local smoothing effect to bound the H 1/2-norm of the approximations locally. This enables us to show that the scheme converges strongly in L 2 (0, T ; L 2 loc (R)) to a weak solution of the equation for initial data in L 2 (R) and some T > 0. Finally we illustrate the method with some numerical examples.