We use 156 044 white dwarf candidates with \geq 5 \sigma significant parallax measurements from the Gaia mission to measure the velocity dispersion of the Galactic disc ; ( \sigma _ { U } , \sigma _ { V } , \sigma _ { W } ) = ( 30.8 , 23.9 , 20.0 ) km s ^ { -1 } .
We identify 142 objects that are inconsistent with disc membership at the > 5 \sigma level .
This is the largest sample of field halo white dwarfs identified to date .
We perform a detailed model atmosphere analysis using optical and near-infrared photometry and parallaxes to constrain the mass and cooling age of each white dwarf .
The white dwarf cooling ages of our targets range from 7 Myr for J1657+2056 to 10.3 Gyr for J1049 - 7400 .
The latter provides a firm lower limit of 10.3 Gyr for the age of the inner halo based on the well-understood physics of white dwarfs .
Including the pre-white dwarf evolutionary lifetimes , and limiting our sample to the recently formed white dwarfs with cooling ages of < 500 Myr , we estimate an age of 10.9 \pm 0.4 Gyr ( internal errors only ) for the Galactic inner halo .
The coolest white dwarfs in our sample also give similar results .
For example , J1049 - 7400 has a total age of 10.9-11.1 Gyr .
Our age measurements are consistent with other measurements of the age of the inner halo , including the white dwarf based measurements of the globular clusters M4 , NGC 6397 , and 47 Tuc .