About 1,200 people died and 771 survived when the British liner was torpedoed by a German submarine on 7 May 1915 during World War One. One of the largest ships in the world, it was sailing from New York to its home port of Liverpool when it was sunk off the coast of Ireland.
A minute's silence will be held at 14:10 BST - the time of the attack - at a service in Liverpool.
The disaster provoked outrage especially in Britain, with rioters targeting German businesses in Merseyside, Manchester and London.
Public opinion in the US, which had been officially neutral, was said to have changed after the death of about 130 Americans, although it was another two years before the country declared its official entry into the war, in 1917.
Ian Murphy, from Merseyside Maritime Museum, said: In 1915, Lusitania was the world's most famous ship and the jewel in Liverpool's crown.
Her sinking sent shockwaves around the globe and was said to have influenced America's entry to the war.
About 600 people onboard the Lusitania had links with Merseyside.
The Reverend Dr Crispin Pailing, rector of Liverpool, said: A significant number of the crew and passengers had Liverpool connections - there is hardly a street in the Vauxhall area that wasn't affected.”
The ship's owner Cunard has commissioned a memorial plaque, which will be dedicated later during a service at Liverpool Parish Church. Actors Joe McGann and Roy Carruthers will read first-hand accounts from survivors.
A painting by the artist Anthony Brown, whose great-grandfather was on the Lusitania's final voyage, will be put on display for the first time.
The service will be followed by a walk of remembrance to the Lusitania's salvaged propeller, now located at the city's Pier Head.
The disaster will also be commemorated at Cobh in the Republic of Ireland, where many victims were buried after the sinking. Last weekend, a service was held in the Isle of Man from where a fishing boat rescued about 150 people.