Wreaths were laid at Whitehall in London and in other parts of the country including Lincolnshire on Saturday at 9am - the same time as the first wreaths were laid at the Cenotaph in 1921.
The ceremony at the Cenotaph was led by retired Lieutenant General James Bashall, national president of the RBL.
In Skegness, the commemoration was held at the memorial outside St Matthew's Church, attended by members of the local branch of the Royal British Legion.
The two-minutes silence and prayer were led by the Rector of Skegness, the Rev Richard Holden, and the Last Post and Reveille were played by bugler Jackie Parkins. A wreath was laid by RBL member Tony Kelly.
Paul Dixon, chairman of the Skegness branch of the RBL, said: "Today we remember the fallen and their great sacrifice, for they have given us our freedom.
"Without them we wouldn't be here."
RBL member Russell Taylor said the day was especially important for the Skegness branch.
"The commemoration not only marks that the RBL has made it to 100 years but this is also an important year for the Skegness branch, which celebrates its 91st anniversary in June," said Mr Taylor.
"When I joined the branch there was uncertainty it would survive, so to be here today is quite an achievement."
Mr Kelly added: "We are working hard to build membership and make the RBL relevant once again to the military. It is not just a social club as many people think."
The commemoration was also the first official engagement for the new Mayor of Skegness, Coun Trevor Burnham.
It had not been widely publicised that the event was taking place locally due to Covid-19 restrictions. Coun Burnham said: "I am honoured to have been invited to share in this historic occasion and to also represent Skegness Town Council and the community."
After the laying of wreaths, the group visited the Hildreds Centre in Skegness, where a special statue of the Jolly Fisherman in Second World War military uniform had been put on display to mark the occasion.
The statue was made by manager of the Hildreds Centre Steve Andrews and his staff to help the Skegness branch of the Royal British Legion celebrate their 91st anniversary on June 21.
Thousands of people watched the laying of wreaths at the memorial in Skegness which was broadcast live by the Skegness Standard on Facebook.
Among the many comments, former councillor Bob Walker said: "Honour to the Fallen and well done and congratulations to the Royal British Legion. 100 years is a fantastic achievement."
Steven Craig commented: "Respect from Chapel St Leonards."
Denise Whittle said: "God Bless you all."
And Doreen May Crawford commented: "Just rode past and saw the one at Kirton Cenotaph."
The centenary was also celebrated in Wainfleet and Spilsby.
In spilsby, a short service led by canon Peter Coates and the laying of three wreaths at the war memorial.
The wreaths were from local RBL branch, the the Airborne Forces, laid by our President, Ron Worth and the WRAC Association laid by RBL branch secretary Barbara Chandler.
Denis Chandler of the branch said: "Ten members braved the chill and approaching rain to attend. The Last Post, Reveille and the National Anthem were played brilliantly by Gary Cole from the Alford Silver Band.
"My thanks to all who took part, especially the Standard Bearer, Bill Atkins, who did a sterling job for the Branch."
1. 100th anniversary of the Royal British Legion in Skegness
Bugler Jackie Parkins plays the Last Post. Photo: Barry Robinson.
2. 100th anniversary of the Royal British Legion in Skegness
Bugler Jackie Parkins plays the Reveille after the two minutes silence. Photo: JPI Media
3. 100th anniversary of the Royal British Legion in Skegness
Members of the Skegness branch of the Royal British Legion pictured with the Rector of Skegness, the Rev Richard Holden and the Mayor of Skegness Coun Trevor Burnham. Photo: Barry Robinson.
4. 100th anniversary of the Royal British Legion in Skegness
A small group gathered at the memorial in Skegness to mark the 100th anniversary of the Royal British Legion. Photo: Barry Robinson