Let $(M, g)$ be a connected, complete Riemannian manifold. Suppose there exists $r > 0$ such that
\begin{align*}
\mathrm{Ric}(v, v) \geq \frac{n-1}{r^2}\, g(v, v)
\end{align*}
for all $v \in TM$. Then
\begin{align*}
\mathrm{diam}(M, g) := \sup_{p,q \in M} d(p, q) \leq \pi r.
\end{align*}
In particular, $M$ is compact, its universal cover $\widetilde{M}$ has finite diameter, and the fundamental group $\pi_1(M)$ is finite.