A Titanic Memorial Garden - with the names of 1,512 victims etched on
five bronze plaques - is being opened close to where the liner was
launched.
A service is being held in Southampton where the voyage to New York began.
And at the North Atlantic site of the sinking, memorial cruise ship Balmoral is marking the time it hit an iceberg.
The ship has arrived at the site where the Titanic sank 400
services miles (460km) off the coast of Newfoundland on 15 April and
passengers and crew are holding commemorations to mark the tragedy.
Another cruise ship, Azamara Journey, has sailed from New York to take part in the ceremony.
Descendants of the victims are expected at the services, and
will lay wreaths and join in a minute's silence in memory of all those
who died.
The sinking is also being remembered in other parts of the globe
Titanic exhibitions are being hosted in Las Vegas, San Diego, Houston and Singapore.
The world's largest visitor centre opened two weeks ago in
Belfast on the Harland and Wolff slipway where Titanic was built. The
£97m ($153m) building has already attracted more than 45,000 visitors.
In nearby Belfast city centre, the Titanic Memorial Garden was completed this weekend, just in time for the 100th anniversary.
There is no distinction on the memorial between first class
passengers and others on board. The names of the dead are simply listed
in alphabetical order.
Intriguingly, two of the names have an asterisk beside them - Mr Thomas Hart and Mr John Horgan.
Kelly Frizell from Belfast City Council said: "The asterisk
means that somebody was travelling under this passenger's name, but they
weren't the actual passenger in question.
"Whether it's their true identity or not, a life is a life, and they lost their life.
"There's no other way to recognise them.
"We couldn't have left them off."
Then real identities of Thomas Hart and John Horgan remain a Titanic mystery.
Ms Frizell spent almost a year researching the victims.
She said: "This is the first monument with all 1,512 names listed in alphabetical order, so it's very significant.
"It's breathtaking looking at such a loss. It's emotional just looking at it."
The plinth bearing the names is nine metres long. The flowers in the garden were chosen carefully.
Landscape architect Joy Hutchinson said: "We went for a
colour scheme built around blue, white, silver and green, reflecting
water and ice.
"It's to try to encourage a sense of peace and contemplation."
In the past two decades, Titanic has become an
internationally recognised brand with movies, memorabilia and commercial
ventures springing up in different parts of the world.
However, the 100th anniversary is being marked with a series
of solemn events, which recognise the tragic reality of the most famous
maritime disaster in history.
Source: BBC News