Observation of $\psi \left(3686\right)\to 3\varphi$

Using $(2.712\pm 0.014)\times {10}^9\psi \left(3686\right)$ events collected by the BESIII detector operating at the BEPCII collider, we report the first observation of $\psi \left(3686\right)\to 3\varphi$ decay with a significance larger than $10\sigma$. The branching fraction of this decay is determined to be $(1.46\pm 0.05\pm 0.17)\times {10}^{-5}$, where the first uncertainty is statistical and the second is systematic. No significant structure is observed in the $\varphi \varphi$ invariant mass spectra.