Grylls grew up in Donaghadee, Northern Ireland and Bembridge on the Isle of Wight. He is the son of the late Conservative party politician Sir Michael Grylls and Lady Grylls (née Sarah Ford). His maternal grandparents were Patricia Ford, an Ulster Unionist Party MP and Neville Ford who played first-class cricket. He has one sibling...an elder sister, Lara Fawcett, a cardio-tennis coach. In an episode of Man vs. Wild featuring Hollywood actor Will Ferrell, he said his sister gave him the nickname "Bear" when he was just a week old.

Grylls was educated at Eaton House, Ludgrove School, Eton College, and Birkbeck, University of London, where he graduated with a degree, obtained part-time, in Hispanic studies in 2002. He learned to climb and sail from his father at an early age. He earned a second dan black belt in Shotokan karate as a teenager. He now practices Yoga and Ninjutsu. He also became involved in scouting, beginning at age eight, as a cub scout. He speaks English, Spanish, and French. Grylls is Christian, describing his faith as the "backbone" in his life.

Grylls married Shara Grylls (née Cannings Knight) in 2000. They have three sons: Jesse, Marmaduke, and Huckleberry (born 15 January 2009 via natural childbirth on his houseboat).

In December 2008, Grylls suffered a broken shoulder while kite skiing across a stretch of ice during an independent expedition to climb a remote unclimbed peak in Antarctica. Travelling at speeds up to 50 km/h (30 mph), a ski caught on the ice, launching him in the air and breaking his shoulder when he came down.

After leaving school, Grylls considered joining the Indian Army and spent a few months hiking in the Himalayan mountains of Sikkim and West Bengal, Assam. From 1994 to 1997, after passing United Kingdom Special Forces Selection, he served in the part-time United Kingdom Special Forces Reserve, with 21 Regiment Special Air Service, 21 SAS(R), as a trooper, survival instructor and Patrol Medic. He claims that he served in North Africa twice. In 1996, he suffered a freefall parachuting accident in Kenya. His canopy ripped at 1,600 feet (500 m), partially opening, causing him to fall and land on his parachute pack on his back, which partially crushed three vertebrae. Grylls later said: "I should have cut the main parachute and gone to the reserve but thought there was time to resolve the problem". According to his surgeon, Grylls came "within a whisker" of being paralysed for life and at first it was questionable whether he would ever walk again. Grylls spent the next 18 months in and out of military rehabilitation at Headley Court before being discharged and directing his efforts into trying to get well enough to fulfil his childhood dream of climbing Mount Everest.

In 2004, Grylls was awarded the honorary rank of Lieutenant Commander in the Royal Naval Reserve.

On 16 May 1998, Grylls achieved his childhood dream (an ambition since his father gave him a picture of Everest when he was eight) and a record, as the youngest Briton, at 23, to summit Mount Everest, just eighteen months after injuring his back. However, James Allen, an Australian/British climber who ascended Everest in 1995 with an Australian team, but who has dual citizenship, beat him to the summit at age 22. The feat has since been surpassed by Jake Meyer and, at age 19, by Rob Gauntlett.

Grylls' expedition involved nearly four months on Everest's southeast face: From his first reconnaissance climb on which he fell in a crevasse and was knocked unconscious, regaining consciousness to find himself swinging on the end of a rope, to the weeks of acclimatisation climbs involving climbing up and down the South Face, negotiating the Khumbu icefall (a frozen river), the Western Cwm glacier, and a 5000 foot wall of ice called the Lhotse face, to the gruelling ascent with the ex-SAS soldier Neil Laughton, involving climbing for hours in the night, that took him past extreme weather, fatigue, dehydration, last-minute illness, sleep deprivation and almost running out of oxygen inside the death zone where air is three times thinner than at sea level.

To prepare for climbing at such high altitudes in the Himalayas, in 1997, Grylls became the youngest Briton to climb Ama Dablam, a peak described by Sir Edmund Hillary as "unclimbable".

Circumnavigation of the UK

In 2000, Grylls, led the first team to circumnavigate the UK on a personal watercraft or jet ski, taking about 30 days, to raise money for the Royal National Lifeboat Institution (RNLI). He also rowed naked for 22 miles in a homemade bathtub along the Thames to raise funds for a friend who lost his legs in a climbing accident.

Crossing the North Atlantic

Three years later, he led a team of five, including his childhood friend, SAS colleague, and Mount Everest climbing partner Mick Crosthwaite, on the first unassisted crossing of the north Atlantic Arctic Ocean, in an open rigid inflatable boat. Battling force 8 gale winds, hypothermia, icebergs and storms in an eleven-metre-long boat through some of the most treacherous stretches of water in the world including the Labrador Sea, the Denmark Strait, and the stretch made famous by The Perfect Storm, Grylls and his team were just barely able to finish the journey from Halifax, Nova Scotia to John o' Groats, Scotland.

Paramotoring over Angel Falls

In 2005, Grylls led the first team ever to attempt to paramotor over the remote jungle plateau of the Angel Falls in Venezuela, the world's highest waterfall. The team was attempting to reach the highest, most remote tepuis.

Dinner party at altitude

In 2005, alongside the balloonist and mountaineer David Hempleman-Adams and Lieutenant Commander Alan Veal, leader of the Royal Navy Freefall Parachute Display Team, Grylls created a world record for the highest open-air formal dinner party, which they did under a hot-air balloon at 25,000 feet, dressed in full mess dress and oxygen masks. To train for the event, he made over 200 parachute jumps. This was in aid of The Duke of Edinburgh's Award and The Prince's Trust.

Paramotoring over the Himalayas

In 2007, Grylls claimed to have broken a new world record by flying a Parajet paramotor over the Himalayas, higher than Mount Everest. Grylls took off from 14,500 feet, 8 miles south of the mountain. Grylls reported looking down on the summit during his ascent and coping with temperatures of −60 °C . He endured dangerously low oxygen levels and eventually reached 29,500 feet, almost 10,000 feet higher than the previous record of 20,019 feet. The feat was filmed for Discovery Channel worldwide as well as Channel 4 in the UK.

While Grylls initially planned to cross over Everest itself, the permit was only to fly to the south of Everest, and he did not traverse Everest out of risk of violating Chinese airspace.

Longest indoor freefall

Grylls, along with the double amputee Al Hodgson and the Scotsman Freddy MacDonald, set a Guinness world record in 2008 for the longest continuous indoor freefall. The previous record was 1 hr 36 mins by a US team. Grylls, Hodgson, and MacDonald, using a vertical wind tunnel in Milton Keynes, broke the record by a few seconds. The attempt was in support of the charity Global Angels.

Northwest Passage Expedition

In August 2010 Grylls lead a team of five to take an ice-breaking rigid-inflatable boat (RIB) through of the ice strewn Northwest Passage. The expedition intended to raise awareness of the effects of global warming and to raise money for children's charity Global Angels.

Grylls entered television work with an appearance in an advertisement for Sure deodorant, featuring his ascent of Mount Everest. Grylls has been a guest on television programs, including Friday Night with Jonathan Ross, The Oprah Winfrey Show, Late Night with Conan O'Brien, The Tonight Show with Jay Leno, Attack of the Show, The Late Show with David Letterman, Jimmy Kimmel Live! and Harry Hill's TV Burp. Grylls recorded two advertisements for Post's Trail Mix Crunch Cereal, which aired in the US from January 2009. He also appeared as a distinguished instructor in Dos Equis' Most Interesting Academy in a webisode named "Survival in the Modern Era". He appeared in a five-part web series that demonstrates urban survival techniques and features Grylls going from bush to bash. He also has marketed the Alpha Course, a course on the basics of the Christian faith. Warner Bros. asked Grylls to appear in its remake of the film Clash of the Titans.

Grylls is a bestselling author. Grylls' first book, titled Facing Up, went into the UK top 10 best-seller list, and was launched in the USA entitled The Kid Who Climbed Everest. About his expedition and achievements climbing to the summit of Mount Everest. Grylls' second book Facing the Frozen Ocean was shortlisted for the William Hill Sports Book of the Year Award 2004. His third book was written to accompany the series Born Survivor: Bear Grylls. (Released in America in April 2008 to the Man vs. Wild Discovery television show) It features survival skills learned from some of the world's most hostile places. This book reached the Sunday Times Top 10 best-seller list.

He has a series of children's adventure survival books titled: Mission Survival: Gold of the Gods, and Mission Survival: Way of the Wolf. His latest book is an extreme guide to outdoor pursuits, titled Bear Grylls Outdoor Adventures.

Escape to the Legion

Grylls filmed a four-part TV show in 2005, called Escape to the Legion, which followed Grylls and eleven other UK "recruits" as they took part in a shortened re-creation of the French Foreign Legion's basic desert training in the Sahara. The show was broadcast in the UK on Channel 4, and in the USA on the Military Channel. In 2008, it was repeated in the UK on the History Channel.

Born Survivor/Man vs. Wild

Grylls hosts a series titled Born Survivor: Bear Grylls for the British Channel 4 and broadcast as Man vs Wild in Australia, Canada and the U.S.A., and as Ultimate Survival on the Discovery Channel in Europe, Asia, and Africa. The series features Grylls dropped into inhospitable places, showing viewers how to survive. The second season premièred in the US on 15 June 2007, the third in November 2007, and the fourth in May 2008. Grylls is currently filming the sixth season in 2010.

The show has featured stunts including Grylls climbing cliffs, parachuting from helicopters, balloons, and planes, paragliding, ice climbing, running through a forest fire, wading rapids, eating snakes, wrapping his urine-soaked t-shirt around his head to help stave off the desert heat, drinking urine saved in a rattlesnake skin, drinking fecal liquid from elephant dung, wrestling alligators, field dressing a camel carcass and drinking water from it, eating various "creepy crawlies" [insects], utilizing the corpse of a sheep as a sleeping bag and flotation device, free climbing waterfalls and using a bird guano/water enema for hydration. Grylls also regales the viewer with tales of adventurers stranded or killed in the wilderness.

In some of the earlier episodes, Man vs. Wild / Born Survivor was criticized by some sources for misleading viewers about some of the situations in which Grylls finds himself. Discovery and Channel 4 television subsequently pledged production and editing transparency and clarification related to the criticism.

Worst Case Scenario

Grylls' latest project is titled Worst Case Scenario and airs on Discovery in the USA. It is based on the popular books of the same name.

On 17 May 2009, The Scout Association announced Grylls would be appointed Chief Scout following the end of Peter Duncan's five year term in July 2009. He was officially made Chief Scout at Gilwell 24 on 11 July 2009 in a handover event featuring Peter Duncan in front of a crowd of over 3,000 Explorer Scouts. He is the tenth person to hold the position and the youngest Chief Scout since the role was created for Robert Baden-Powell in 1920.

Many of Grylls' expeditions and stunts have raised money for charitable organisations. Grylls is an ambassador for The Prince's Trust, an organisation which provides training, financial, and practical support to young people in the United Kingdom. He is also vice president for The JoLt Trust, a small charity that takes disabled, disadvantaged, abuse or neglected young people on challenging month-long expeditions.

Global Angels, a UK charity which seeks to aid children around the world, were the beneficiaries of his 2007 attempt to take a powered para-glider higher than Mount Everest. Grylls's attempt to hold the highest ever dinner party at 25,000 feet was in aid of The Duke of Edinburgh's Award Scheme, and launched the 50th anniversary of the Awards. His attempt to circumnavigate Britain on jet skis raised money for the Royal National Lifeboat Institution. Grylls' Everest climb was in aid of SSAFA Forces Help, a British-based charitable organisation set up to help former, and serving members of the British Armed Forces, and their families and dependents. His 2003 Arctic expedition detailed in the book Facing the Frozen Ocean was in aid of The Prince's Trust. His 2005 attempt to para-motor over the Angel Falls was in aid of the charity Hope and Homes for Children. Grylls is continuing his fundraising work for Global Angels in August 2010 by undertaking an expedition through the Northwest Passage in a rigid inflatable boat.

Outside of TV, Grylls sometimes works as a motivational speaker. Grylls has his own outdoor survival clothing range produced by British manufacturer Craghoppers.