She will also take on a role as non-executive director of the RadioCentre, the umbrella organisation for the RAB, the Commercial Radio Companies Association and chart company Hit 40 UK.
King's appointment is the first part of the relaunch of the RAB, which will take place across the coming months.
King began her career in sales roles at The Observer and The Guardian. She then moved into commercial radio where she spent six years heading Capital Radio.
She had a brief stint as managing director of TSMS the former ITV sales house before becoming the first managing director of Yahoo! UK & Ireland in 1999, leading and expanding the London-based team before taking up the European position. She left Yahoo! in June 2004 to spend more time with her family.
Andrew Harrison, chief executive of the RadioCentre, said: "[Martina] is well known across the sector and with a track record of leading revenue and audience growth in radio. Her knowledge and experience from radio and new media sectors will be of huge value to the RadioCentre, the RAB and the Commercial Radio industry as a whole."
King said: "Radio has always been one of my biggest passions and I'm looking forward to getting back on board. Radio is flexible and ubiquitous, and has a fantastic future at the heart of digital convergence. It's an exciting time and I'm looking forward to working with Andrew and his team helping deliver an exciting future for commercial radio in the digital age."
Harrison was confirmed as the chief executive of the RadioCentre in May of last year.