Another German, Tatjana Huefner, captured the silver and the first women's luge medal ever won by an American went to third-place finisher Erin Hamlin.
This was the 14th time the women have contested a luge event at the Olympics and the gold medal has gone to a German nine times, including the last five in a row.
Geisenberger won the bronze medal in the event four years ago while Huefner added her silver to the gold she won in Vancouver and a bronze she took home from Turin.
The new Olympic champion turned in the fastest run in all four of the trips down the canyon of ice, where the contestants travel at more than 130 kilometers an hour.
Geisenberger's first run on Tuesday, her third of the competition, took just 49.765 seconds. That time was a track record and gave her a lead of more than a full second heading into the final run.
Hamlin was in third place heading into Tuesday's competition and she put together two solid efforts to maintain that position. She finished .238 of a second behind Huefner for the four runs.