A Marilyn is a hill of any height with a drop of 150 metres or more on all sides. In other words, a relatively high hill. The British Marilyns are all listed in a book called The Relative Hills of Britain (RHB) by Alan Dawson, published by Cicerone Press in April 1992. Details of subsequent changes have been published in a series of update sheets.
The total number of Marilyns is currently 1556. Recent changes are the promotion of Sithean Mor (13A), Creag an Amalaidh (16D) and Kirriereoch Hill (27B) to Marilyns, and the demotion of Cruim Leacainn (4A), Stob na Boine Druim-fhinn (19C), Troweir Hill (27B) and Swyre Head (41). Details up to April 2014 are available in the latest update to RHB.
On 13 October 2014, Rob Woodall and Eddie Dealtry climbed Stac an Armin and then Stac Lee, and so became the first people to climb all the Marilyns. On 17 October 2015 twelve people reached the summit of Stac Lee and the following day eleven of them climbed Stac an Armin, with Michael Earnshaw and Alan Whatley becoming the third and fourth people to climb all the Marilyns.