Bridge will be responsible for leading a review of the organisation's agency arrangements, and will take control of an upcoming pitch handled by Oystercatchers.
The high-profile marketer's appointment by the charity signals a clear intention to make a step change in Save the Children's approach to marketing and communications.
A charity spokesperson said: "We're now looking at all our marketing communications with a view to taking a more joined-up approach across areas old and new, with the aim of waking up Britain."
Separately, the charity has seconded Adrian Lovett to chair Save the Children's global 'Every One' campaign and the '1 Goal' campaign committee.
Bridge was among a series of senior departures at M&S in March 2008, as part of a management restructure at the retail business.
She was credited with overseeing the launch of the 'Your M&S' work in 2006, which played a key part in the retailer's marketing strategy as it looked to reposition itself in the UK.
She had been with M&S since 2001, prior to which she worked at Publicis, where she was in charge of the Woolwich account. She had previously held various marketing roles at United Biscuits for five years, after starting her career with 10 years at Unilever.
Save the Children is leading a response team for the two million people affected by the devastating earthquake in Haiti, with donations being sought at www.savethechildren.org.uk/haiti