From the middle of the 1880s until the commencement of the Great War 1914-’18 the first-class cruiser was an vital component of the British battlefleet. This was a period in which technology and tactics evolved at an extremely rapid pace, forming the material basis for Sir John Fisher’s ‘Dreadnought Revolution’, in which cruiser qualities of speed, range and offensive power were greatly prized. Throughout this era enormous sums were spent on such types: they were frequently longer than and cost almost as much as their battleship contemporaries, while carrying a near-equivalent armament and possessing significant advantages in both speed and endurance. Despite these capabilities, British first-class cruisers, especially those of the 1890s, are comparatively rarely examined by historians. This thesis fills the gap in the historiography by examining the place and development of the type in the Royal Navy from 1884-1909, and illustrates how they would progress from being a trade-defence vessel, to a genuine alternative to the battleship, and would ultimately form the basic inspiration for all of the service’s first all-big-gun capital ships. It begins by assessing the origins of the type in the mid-Victorian era and considers how the contemporary strategic position and materials drove vessel characteristics, resulting in the development of the first unofficially termed ‘battle-cruisers’ to counter the threat of a Franco-Russian guerre de course employing dedicated raiding types and armed high-speed liners. Following a dramatic advance in the protective capacity of armour that occurred in the mid-1890s, it is shown how the first-class cruiser would gain a fighting ability at least equal to their battleship contemporaries in addition to their continued utility in the trade-defence role, and how latterly, these characteristics would become the cornerstone of Sir John Fisher’s planned radical transformation of the service in the first decade of the 20th Century.