She is expected to leave at the end of June. The company is looking for a replacement.
After four years as the managing director of Yahoo! UK and Ireland, King was promoted in early 2003 to the European role with a brief to export learnings from the UK to other markets. Fru Hazlitt, formerly Yahoo!'s sales and marketing director, replaced King as the managing director in the UK.
King, a former managing director of Capital Radio and ITV's sales house TSMS, is expected to spend some time with her family while looking for a new role.
She said Yahoo! had "continued to build our successful and expanding European operations". 2003 was Yahoo!'s most successful year, with profits up to $296 million.
King said: "The best time to leave a job is on a high. This is such a moment for Yahoo! and I believe that it is the right time for me to leave."