David Cameron has encouraged the public to show their support for "extraordinary men and women" of the military for Armed Forces Day today.
Nottingham will host a major national event, including an aerial display featuring the Red Arrows and a parachute team.
The Prime Minister said: "Armed Forces Day is about reminding the British people that everyday, as we go about our business, there are extraordinary men and women all over the world, and indeed right here at home, who risk their lives for our safety and security.
"Let us show everyone in our Armed Forces just how proud we are of everything that they do."
The fifth national Armed Forces Day will begin today with an artillery regiment firing a volley of gun blasts at Nottingham Castle.
Further celebrations are planned across the UK.