This dissertation describes a direct measurement of the W boson total decay width, using the DZero detector at the Fermilab Tevatron Collider. The measurement uses an integrated luminosity of 177.3 pb-1 data, collected during the 2002-2003 run. The width is determined from the shape of the transverse mass distribution, MT, by fitting the data in the tail region 100<MT<200 GeV. The result is Gamma_{W}=2.011 +- 0.093 (stat) +- 0.107 (syst) GeV.