arXiv:0912.4715v1 [hep-th] 23 Dec 2009 TBA and Y-system for planar AdS 4 /CFT 3 Diego Bombardelli a , Davide Fioravanti a and Roberto Tateo b ∗ a INFN-Bologna and Dipartimento di Fisica, Universit` a di Bologna, Via Irnerio 46, 40126 Bologna, Italy. b Dip. di Fisica Teorica and INFN, Universit` a di Torino, Via P. Giuria 1, 10125 Torino, Italy. Abstract We conjecture the set of asymptotic Bethe Ansatz equations for the mirror model of the AdS 4 ×CP 3 string theory, corresponding to the planar N = 6 superconformal Chern-Simons gauge theory in three dimensions. Hence, we derive the (vacuum energy) thermodynamic Bethe Ansatz equations and the Y-system describing the direct AdS 4 /CFT 3 string theory. ∗ e-mails: bombardelli@bo.infn.it, fioravanti@bo.infn.it, tateo@to.infn.it.