Sirens sounded at midday to signal the start of a minute's silence held all over the country.
Since records began, 2,486 firefighters are known to have died duty serving their communities and keeping people safe.
The event is held organised by the Firefighters Memorial Trust and by the Fire Brigades Union.
Colin Livett, chair of the trust, said: “Fire does not distinguish between men, women or children - race, religion or creed. Neither do firefighters, they answer the call and do their duty. Some pay the ultimate sacrifice.”
FBU general secretary Matt Wrack said: “Firefighters Memorial Day is about honouring the courage and bravery of the men and women of the fire service.
"These are highly skilled professionals who selflessly put themselves in the line of danger to protect others. We owe them so much, and this is a day to remember what they give their communities."
He added: “Firefighters understand the risks associated with their job but they do expect to come home safe after each shift. Sadly, this is not always the case. It’s important that none of us forget the sacrifice these men and women have made in order to keep people safe.
“We hope this day will bring comfort and strength to the families and loved ones of those who have been lost.”