Katharine Viner has been appointed the editor-in-chief of the Guardian, the first woman to run the newspaper in its 194-year history. Viner, currently deputy editor of the Guardian and editor-in-chief of Guardian US, will take up the role in the summer from incumbent Alan Rusbridger, who is to stand down after 20 years.

The Scott Trust, the ultimate owner of the Guardian, which safeguards the title’s editorial future and independence, made the announcement on Friday after members of the board conducted final interviews with two shortlisted candidates. Viner will become only the 12th editor since the paper was founded in May 1821.

She won the overwhelming support of Guardian and Observer staff in an indicative ballot held earlier this month. Fifty-three per cent of those who voted backed Viner, with a first-choice vote of 438 in the single transferrable vote system used for the ballot.

Commenting on her appointment, Viner said: “Being editor-in-chief of the Guardian and Observer is an enormous privilege and responsibility, leading a first-class team of journalists revered around the world for outstanding reporting, independent thinking, incisive analysis and digital innovation.”

Saying she was “honoured” to succeed Rusbridger, she said: “Building on his track record, I intend to lead a media organisation that is bold, challenging, open and engaging. It will be a home for the most ambitious journalism, ideas and events, setting the agenda and reaching out to readers all around the world.”

Rusbridger said: “Kath rose up through the Guardian as an inspired magazine and features editor. She took Australia by storm before heading up the Guardian’s American operation. She will bring immense experience, flair, warmth, imagination and formidable energy to her new role as editor of the Guardian.”

Liz Forgan, outgoing chair of the Scott Trust, which announced the decision after a seven-hour meeting, said: “Kath shone through in what was a tremendously strong lineup of candidates. In her 18 years at the Guardian, she has done almost every editorial job in the organisation, including running Guardian US and Guardian Australia, and has shown herself to be an inspiring and courageous leader. She has embraced the huge changes in the industry with creativity and relish whilst bringing with her a deep commitment to the Guardian’s traditions of plural, liberal journalism.

“This has been a thorough, transparent and, for the first time, international process. We considered a very broad range of candidates across geographies, disciplines and backgrounds – including all those who took part in the editorial hustings – in our determination to leave no stone unturned in the search for the best person to lead this now global and much respected media organisation.”

Viner becomes the only woman at the top of a daily quality title in the UK. She joins a small group of women editing leading British newspapers: Lisa Markwell, editor of the Independent on Sunday, Victoria Newton, the editor of the Sun on Sunday, Sarah Sands at the Evening Standard, and Dawn Neesom at the Star.

In total, 26 people applied for the job in a process conducted by the Scott Trust in conjunction with an executive search firm.

The NUJ chapel at the titles welcomed Viner’s appointment. Brian Williams, father of the chapel, said: “We have a unique process for the appointment of our editor-in-chief. The indicative ballot of editorial staff, in which 839 Guardian and Observer journalists voted, and the hustings which preceded it, is now firmly cemented at the heart of that process. The open and transparent system ... gives our incoming editor an unparalleled position in the media and we look forward to working with her.”

Viner joined the Guardian in 1997 and has been a deputy editor of the title as well as editing the Saturday edition of the newspaper from 2008 until 2012. She was then given responsibility for launching the Guardian’s Australian operation, building it to a team of 40 over 16 months. Last summer, she moved to New York to take the role of editor-in-chief of Guardian US. She has held a wide range of roles including editor of G2, deputy women’s editor, and editor of Weekend magazine.

Educated at Ripon Grammar School and the University of Oxford, Viner spent three years at the Sunday Times before joining the Guardian. Her first job was with Cosmopolitan magazine.

Rusbridger is to take up the role of chairman of the Scott Trust, the ultimate parent of the Guardian and Observer newspapers, at the start of 2016, replacing Liz Forgan when she ends her term as chair. During his tenure, the Guardian was awarded the highest accolade in US journalism, the Pulitzer prize for public service, for its exposure of the surveillance activities of the US National Security Agency, following leaks by Edward Snowden.