We demonstrate integrated lithium niobate (LN) microring resonators with $Q$ factors close to the intrinsic material absorption limit of LN. The microrings are fabricated on pristine LN thin-film wafers thinned from LN bulk via chemo-mechanical etching without ion slicing and ion etching. A record-high $Q$ factor up to ${10}^8$ at the wavelength of 1550 nm is achieved because of the ultra-smooth interface of the microrings and the absence of ion-induced lattice damage, indicating an ultra-low waveguide propagation loss of $\sim 0.0034\mathrm{dB}/\mathrm{cm}$. The ultra-high $Q$ microrings will pave the way for integrated quantum light source, frequency comb generation, and nonlinear optical processes.