  Using $(2.712\pm0.014)\times 10^9$ $\psi(3686)$ events collected by the
BESIII detector operating at the BEPCII collider, we report the first
observation of $\psi(3686)\to 3\phi$ decay with a significance larger than
10$\sigma$. The branching fraction of this decay is determined to be
$(1.46\pm0.05\pm0.17)\times10^{-5}$, where the first uncertainty is statistical
and the second is systematic. No significant structure is observed in the
$\phi\phi$ invariant mass spectra.
