Konta had hoped to become the first British woman to play in a Wimbledon singles final since 1977.
But Williams couldn't be beaten. The American won 6-4 6-2 on Centre Court and will now face Spain's Garbine Muguruza.
Williams is the oldest Grand Slam singles finalist since Martina Navratilova finished runner-up at Wimbledon in 1994.
Johanna Konta's dream of a playing in a Wimbledon final ended as she was beaten in straight sets by five-time champion Venus Williams in the semi-final.