  Using a sample of $1.31$ billion $J/\psi$ events accumulated with the BESIII
detector at the BEPCII collider, we report the observation of the decay $J/\psi
\rightarrow \phi\pi^{0}$, which is the first evidence for a doubly
Okubo-Zweig-Iizuka suppressed electromagnetic $J/\psi$ decay. A clear structure
is observed in the $K^{+} K^{-}$ mass spectrum around 1.02 GeV/$c^2$, which can
be attributed to interference between $J/\psi \rightarrow \phi\pi^{0}$ and
$J/\psi \rightarrow K^{+}K^{-}\pi^{0}$ decays. Due to this interference, two
possible solutions are found. The corresponding measured values of the
branching fraction of $J/\psi \to \phi\pi^{0}$ are $[2.94 \pm
0.16\text{(stat.)} \pm 0.16\text{(syst.)}] \times 10^{-6}$ and $[1.24 \pm
0.33\text{(stat.)} \pm 0.30\text{(syst.)}] \times 10^{-7}$.
