The 23-time Grand Slam champion had been the favourite despite only contesting her fourth tournament since giving birth in September.
However, Kerber comfortably beat the record-chasing American 6-3 6-3 in just over an hour on Centre Court.
The German 11th seed made just five unforced errors compared to her opponent's 24 en route to reversing the result of the 2016 final.
Kerber's comfortable victory saw her pick up the third Grand Slam title of her career, adding to her Australian and US Open triumphs in 2016.
In addition, Kerber becomes the first German to win a Wimbledon singles title since Steffi Graf in 1996.