Given any closed Riemannian manifold $M$, we construct a reversible diffusion process on the space ${\mathcal P}(M)$ of probability measures on $M$ that is (i) reversible w.r.t.~the entropic measure ${\mathbb P}^β$ on ${\mathcal P}(M)$, heuristically given as $$d\mathbb{P}^β(μ)=\frac{1}{Z} e^{-β\, \text{Ent}(μ| m)}\ d\mathbb{P}^*(μ);$$ (ii) associated with a regular Dirichlet form with carré du champ derived from the Wasserstein gradient in the sense of Otto calculus $${\mathcal E}_W(f)=\liminf_{g\to f}\ \frac12\int_{{\mathcal P}(M)} \big\|\nabla_W g\big\|^2(μ)\ d{\mathbb P}^β(μ);$$ (iii) non-degenerate, at least in the case of the $n$-sphere and the $n$-torus.