GPS velocities from sites near to the Fairweather fault in southern Alaska are combined with line length data from geodetic surveys by the U. S. Geological Survey (USGS) to estimate the slip rate and locking depth of the Fairweather fault using dislocation theory. We perform a weighted least-squares inversion of the geodetic data and obtain a best-fitting slip rate of 45.6 ¿ 2.0 mm/yr and locking depth of 9.0 ¿ 0.8 km. The slip rate we estimate is one of the highest observed across any strike slip fault. We also include the Dalton Creek segment of the Denali fault in our model and estimate a slip rate of 3.8 ¿ 1.4 mm/yr for this section of the fault. This is substantially lower than the rate observed for the Denali fault segment to the northwest, which ruptured in the November 3, 2002 MW 7.9 Denali fault earthquake.