The tau lepton lifetime is measured with the L3 detector at LEP using the c
omplete data taken at center-of-mass energies around the Z pole resulting i
n tau(tau) = 293.2 +/- 2.0 (stat) +/- 1.5 (syst) fs. The comparison of this
result with the muon lifetime supports lepton universality of the weak cha
rged current at the level of Mix per mille. Assuming lepton universality, t
he value of the strong coupling constant, alpha(s), is found to be alpha(s)
(m(r)(2)) = 0.319 +/- 0.015 (exp) +/- 0.014 (theory). (C) 2000 Elsevier Sci
ence B.V. All rights reserved.