  We report a measurement of the average $B$-hadron lifetime using data
collected with the SLD detector at the SLC in 1993. An inclusive analysis
selected three-dimensional vertices with $B$-hadron lifetime information in a
sample of 50k $Z^{0}$ decays. A lifetime of $1.564\pm0.030\,(\rm stat)\pm
0.037\,(\rm syst)$~ps was extracted from the decay length distribution of these
vertices using a binned maximum-likelihood method.
