Measurements of the $CP$ violating phase $\phi_s$ at LHCb

The measurement of the mixing-induced CP-violating phase $\phi_s$ in the Bs-Bsbar system is one of the key goals of the LHCb experiment. It has been measured at LHCb exploiting the Run I data set and using several decay channels. The poster shows the most recent results obtained analyzing $B_s^0 \to J/\psi K^+K^-$ candidates in the mass region above the $\phi(1020)$ resonance. The poster also shows previous measurements obtained analyzing the golden channel, $B_s^0 \to J/\psi K^+K^-$ in $\phi(1020)$ region, and $B_s^0 \to J/\psi \pi^+ \pi^-$. Finally, a combination of those studies is presented.