Gattung was born in Wellington, the eldest of four daughters. She was educated at McKillop College, Rotorua, the University of Waikato (graduating with a Bachelor of Management Studies in marketing) and Victoria University of Wellington (graduating with a Bachelor of Laws).
Gattung worked in senior marketing roles at National Mutual and at the Bank of New Zealand before taking up a similar role at Telecom New Zealand. In April 1996, she became Telecom's Group General Manager Services. In October 1999, she took over from Rod Deane as Telecom's CEO of the telecommunications business with a $5billion turnover operating in New Zealand and Australia and listed on the NZX, ASX and NYSE. Gattung was the first woman to run a large New Zealand public company. During her tenure as CEO Gattung led Telecom through world-changing technology developments and the evolution of the business from a traditional Telco to the number one IT provider in New Zealand.
Gattung resigned her position at Telecom in 2007.
From July 2008 to March 2011, Gattung was the inaugural Chair of Wool Partners International applying her leadership skills, international business experience, marketing and branding expertise to lead the company’s drive to reinvigorate the international market for New Zealand’s strong wools.
Following her passion for books and reading Gattung was also the Chair of the New Zealand Advisory Group for the Frankfurt Book Fair 2012.
Gattung was appointed Chair of insurer AIA Australia in 2010, and also chairs the online education content provider Telco Technology Services  and CoOfWomen. In 2013, Gattung, alongside Cecilia Robinson and Nadia Lim, co-founded food delivery business My Food Bag. Operating in New Zealand the company has grown very quickly with turnover exceeding $100 million.
Gattung has been involved with a number of not-for-profit and philanthropic interests, including being co-founder and trustee of the World Women Charitable Trust, the Eva Doucas Charitable Trust, Patron of the Cambodia Charitable Trust and Chair of the Wellington Board of the Society for the Prevention of Cruelty to Animals (SPCA).
In 2010, Gattung published an autobiography, Bird on a Wire.
Awards and recognition
In 2015 Gattung was made a Companion of the New Zealand Order of Merit for services to business and philanthropy. In August 2015 Theresa was inducted into the Marketing Hall of Fame at the 2015 TVNZ Marketing Awards.
Gattung has been named in Fortune magazine's list of the 50 most powerful women in international business several times, and in 2006 the Forbes list of "The World's 100 Most Powerful Women" ranked Gattung at number 49.
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