We consider the problem of nonstochastic control with a sequence of quadratic losses, i.e., LQR control. We provide an efficient online algorithm that achieves an optimal dynamic (policy) regret of Õ(max{n 1/3 TV(M1:n) 2/3 , 1}), where TV(M1:n) is the total variation of any oracle sequence of Disturbance Action policies parameterized by M1, ..., Mn -chosen in hindsight to cater to unknown nonstationarity. The rate improves the best known rate of Õ( n(TV(M1:n) + 1)) for general convex losses and we prove that it is information-theoretically optimal for LQR. Main technical components include the reduction of LQR to online linear regression with delayed feedback due to Foster and Simchowitz (2020), as well as a new proper learning algorithm with an optimal Õ(n 1/3 ) dynamic regret on a family of "minibatched" quadratic losses, which could be of independent interest.