Rometty joined IBM in 1981 as a systems engineer, moving quickly up the management ladder. In 2002 she was a prominent backer of the move to buy business consulting firm PricewaterhouseCoopers Consulting for $3.5bn, and is widely credited with making that deal work by merging two very different cultures.
Since 2009 she has been senior vice president for sales, marketing and strategy, leading IBM's drive to increase its business in emerging markets outside the US. These markets now account for 23% of IBM's total revenue. Romitty has said her job was "not about capturing markets, it's about making new markets".
Rometty was placed at number 8 on the Fortune 500 list of the most powerful female executives of 2010. Her appointment should take her further up the rankings when the list is updated for this year. But let's look at those top 10 women in the boardroom.