The first oil-fired cruiser depends on launch and commissioning dates

Which cruiser class was the first to use oil-fired boilers?

Possibly an American class, but the answer depends on whether launch or commissioning establishes priority and requires more research.

The competing claims to priority require checking the chronology. British oil-fired destroyers from 1904 provide background, while Italian possibilities also need checking. The tentative recollection is that an American cruiser may have launched first even though a British ship commissioned earlier. Different launch and commissioning dates, together with Britain's faster path into service, can produce competing claims to priority. No definitive class is identified without detailed research.