Conor O’Neill joined the Royal Navy in 1999 as a University Cadet (Warfare). He read Modern History and Politics at Wadham College, Oxford and completed at Masters in 2004. Following Fleet Navigating Officer’s Course in 2007, he joined HMS CUMBERLAND, then HMS CHATHAM, deploying to the Arabian Gulf in 2008 on Operation TELIC. Having returned to the UK, he served on the staff of Flag Officer Sea Training (Mine Warfare and Patrol Vessels) as a navigation sea-rider before assuming Command of HMS TRACKER and Oxford URNU in September 2009. Promoted to Lieutenant Commander in October 2011, he assumed Command of the Faslane Patrol Boat Squadron and HMS PURSUER on UK force protection duties. Following PWO training the following year, he joined HMS SOMERSET in July 2013, deploying on Op KIPION in January 2014.

 He joined the Defence Engagement Strategy staff in the Ministry of Defence in November 2014 as a desk officer in the Strategic Plans team. Highlights there included taking the UK-US Strategic Effects and Force Alignment Board from pilot study to reality, the development of Defence Engagement doctrine, and policy support to the 2015 SDSR. Returning to sea in April 2016, he assumed Command of MCM 2 Crew 1, first in HMS QUORN and then HMS HURWORTH. Selected for promotion to Commander and further Sea Command in July 2016, he enjoyed a short tour in the South Atlantic in Command of the Falkland Islands Patrol Vessel, HMS CLYDE, towards the end of the Austral Winter, patrolling both the Falkland Islands and South Georgia. He then assumed Command of HMS MONTROSE in April 2017 at the start of her generation from upkeep, leading her to a successful return to the front line in mid 2018. After a short period of National Tasking in the Baltic Sea, she deployed to Bahrain at the end of 2018 as the first forward deployed major warship since the 1970s, via a near global deployment across the South Pacific and Asia, including operations in the South and East China Seas, as well as the Indian Ocean.

After completing the Advanced Command and Staff Course, he undertook a short assignment within Navy Command Resources and Plans, before joining the new Strategic Plans team under the Assistant Chief of the Naval Staff, supporting the development of the RN Strategy, Strategic Prioritisation and the implementation of the 2021 Integrated Review.