  We demonstrate an on-chip Yb3+-doped lithium niobate (LN) microdisk laser.
The intrinsic quality factors of the fabricated Yb3+-doped LN microdisk
resonator are measured up to 3.79x10^5 at 976 nm wavelength and 1.1x10^6 at
1514 nm wavelength. The multi-mode laser emissions are obtained in a band from
1020 nm to 1070 nm pumped by 984 nm laser and with the low threshold of 103
{\mu}W, resulting in a slope efficiency of 0.53% at room temperature.
Furthermore, the second-harmonic frequency of pump light and the sum-frequency
of the pump light and laser emissions are both generated in the on-chip
Yb3+-doped LN microdisk benefited from the strong \c{hi}(2) nonlinearity of LN.
These microdisk lasers are expected to contribute to the high-density
integration of LNOI-based photonic chip.
