The Jiangmen Underground Neutrino Observatory (JUNO) is a multipurpose neutrino detector under construction in China. It is located 700 m underground, 53 km away from eight nuclear reactors. It will use 20 kt of liquid scintillator surrounded by 17,612 20" photomultipliers and 25,600 3" photomultipliers to detect neutrino interactions with a 3% energy resolution at 1MeV. JUNO's main physics goals are the determination of the neutrino mass ordering and the high-precision measurement of $\Delta m^2_{21}$, $\sin^2\theta_{12}$, and $\Delta m^2_{31}$.

I will present how JUNO can measure the reactor antineutrino oscillations to reach a $3\sigma$ sensitivity to the neutrino mass ordering with 6 years of data. JUNO can also measure atmospheric neutrino oscillations to enhance this sensitivity. After 6 years, JUNO will improve the current precision on $\Delta m^2_{21}$, $\sin^2\theta_{12}$, and $\Delta m^2_{31}$ by an order of magnitude, achieving precision well below the sub-percent level.