Vanessa O’Brien is a British mountaineer and an American mountaineer (as a result of her dual nationality), climber, explorer, public speaker and former business executive.

She became the first American woman to climb K2 and the first British woman to climb K2 (as a result of her dual nationality) on 28 July 2017 when she successfully led a team of 12 members to the summit and back on her third attempt, receiving Explorer of the Year by the SES for her efforts in 2018. She is a Fellow of the Royal Geographical Society, Fellow of The Explorers Club, and a Member of The Scientific Exploration Society (SES).

Vanessa climbed the highest peak on every continent, receiving a Guinness World Record setting a record for the fastest time a woman first achieved this goal (295 days). Vanessa has skied the last 111 km to the South and North Poles completing the Explorers Grand Slam in 11 months, becoming the first woman to do so in under a year and the 8th woman in the world. Outside of mountaineering, Vanessa completed the Boston Marathon in 2017, helping to raise money for the American Red Cross, has been shot testing bulletproof clothing at point blank range by Miguel Caballero with a .38 long revolver, and reached 200 mph riding with Mario Andretti at Indianapolis Motor Speedway in 2018.