Admiral Sir Tony Radakin will officially take over the role of Chief Of Defence Staff (CDS) in November, replacing General Sir Nick Carter.
He will become Britain's most senior military official and the first naval officer to be appointed to the role since Admiral Sir Michael Boyce, who was in post between 2001 and 2003.
Reactions to the appointment and congratulations for the current Royal Navy chief have been posted on Twitter.
Adm Radakin overcame competition from Head of Strategic Command General Sir Patrick Sanders and Chief of the General Staff General Sir Mark Carleton-Smith.
In a tweet, the Chief of the General Staff was quick to offer "congratulations".
The CGS said: "The Army wishes him the best of luck in his important role."
Candidates for the outgoing defence chief's job had interviews with Defence Secretary Ben Wallace last month.
Then, Prime Minister Boris Johnson interviewed them, before making his choice and submitting it to the Queen, who ultimately made the appointment.
Armed Forces Minister James Heappey also congratulated Admiral Radakin on his appointment, tweeting: "These are exciting times for our nation's Armed Forces - looking forward to working with him to deliver the Integrated Review & the Government’s vision for #GlobalBritain."
In a statement posted on Twitter, First Sea Lord Sir Tony Radakin said he was "humbled" to be selected.
He said: "It will be an immense privilege to lead our outstanding people who defend and protect the United Kingdom.
"I am honoured to be chosen to lead the Armed Forces in this exciting time and in a period of enormous change."