Munro was born in London but was brought up in Scotland on the family estate of Lindertis near Kirriemuir in Angus. He was an avid hillwalker, and was a founder member of the Scottish Mountaineering Club in 1889. His list of 3,000-foot mountains 1891 was published in the 6th issue of the Scottish Mountaineering Club Journal in 1891. This list caused much surprise in mountaineering circles, as until his list was produced many thought that the number of mountains exceeding this height was around 30, rather than the nearly 300 that he listed. These mountains are now known as Munros and it is a popular hobby to attempt to climb them all.
Hugh Munro never completed his own list. Of his original list he failed to climb one mountain in the Cairngorms (Carn Cloich-Mhuillin), which he was saving to be his last. At the time of his death he had produced a revised version of the list, adding Carn an Fhidhleir, which he had also yet to climb. Sir Hugh is often credited with missing out the Inaccessible Pinnacle of Sgurr Dearg, on the Isle of Skye, a peak which there is no record of his having climbed. However, the "In Pinn" was not included in either of the lists produced during his lifetime, despite being several feet higher than Sgurr Dearg, which was included. The first person to achieve the feat is generally regarded as being the Rev. A. E. Robertson in 1901.
In addition to his mountaineering interests, Munro was well travelled and made trips to Europe, Asia, North America and Africa. He was too old at 58 for military service during World War I but did volunteer work with the Red Cross and cared for injured soldiers in Malta in 1915. After a spell of illness, he rejoined the Red Cross, running a canteen for Allied forces near the front line in France. He died in 1919 aged 63, during the influenza epidemic that followed the war.