Solving the optimal data detection problem in multiple-input multiple-output (MIMO) systems is known to be NP-hard. Moreover, the difficulty is exacerbated when the channel state information is unavailable. In this work we propose a MIMO detector for the two scenarios, namely when the CSI is known and when it is unknown. First, for the case of perfect CSI, we proposed a MIMO detector based on an annealed version of Langevin dynamics. More precisely, we define a stochastic dynamical process whose stationary distribution coincides with the posterior distribution of the data given our observations. This allows us to approximate the maximum a posteriori estimator of the transmitted symbols by sampling from the proposed Langevin dynamic. We carefully craft this stochastic dynamic by gradually adding a sequence of noise with decreasing variance to the trajectories, which ensures that the estimated symbols belong to a pre-specified discrete constellation. Second, for the case of unknown CSI, we propose a joint data detection and channel estimation solution, where we define an annealed Langevin diffusion whose stationary distribution is the joint posterior of the channels and data given noisy observations.