Littorio was laid down at the Ansaldo shipyards in Genoa on October 28th 1934 to commemorate the Fascist Party's March on Rome in 1922. Her sister Vittorio Veneto was laid down the same day. Changes to the design and a lack of armor plating led to delays in the building schedule, causing a three-month slip in the launch date from the original plan of May 1937. Littorio was launched on August 22nd 1937, during a ceremony attended by many Italian dignitaries. She was sponsored by Signora Teresa Ballerino Cabella, the wife on an Ansaldo employee. After her launch, the fitting out period lasted until early 1940. During this time, Littorio's bow was modified to lessen vibration and reduce wetness over the bow. Littorio ran a series of sea trials over a period of two months between October 23rd and December 21st 1939. She commissioned on May 6th, 1940, and after running additional trials that month, she transferred to Taranto where she—along with the Vittorio Veneto—joined the 9th Division under the command of Rear Admiral Carlo Bergamini.
Between August 31st and September 1st 1940, Littorio sortied as part of an Italian force of five battleships, ten cruisers, and thirty-four destroyers to intercept British naval forces taking part in Operation Hats and Convoy MB.3, but contact was not made with either group due to poor reconnaissance and no action occurred.
A similar outcome resulted from the movement against British Operation "MB.5" on September 29th - October 1st; Littorio, four other battleships, eleven cruisers, and twenty-three destroyers had attempted to intercept the convoy carrying troops to Malta.