Froome wrested the jersey -- indicative of the overall leader -- from South African rider Daryl Impey during the ride from Castres to Ax 3 Domaines with a time of 5 hours, 3 minutes, 18 seconds.
The Kenyan-born Briton, considered the favorite for the stage, was dominant on the final climb and put his Sky Procycling team in a commanding position as the 100th edition of the Tour de France moved into the Pyrenees mountain range.
Sky teammate Richie Porte came in second 51 seconds behind Froome, and the pair held first and second place overall at the end of the first day in the mountains.
Stage 8 was a tough one for former Tour champions Alberto Contador, Andy Schleck and Cadel Evans. Each fell further off the pace, with Contador dropping to seventh place overall, trailing by 1 minute, 46 seconds.
Rounding out the Top 5 stage finishers Saturday were Alejandro Valverde Belmonte, Bauke Mollema and Laurens Ten Dam.
Sunday's ninth stage is a 102-mile ride from Saint-Girons to Bagneres-de-Bigorre.