A 100-year-old wreck site has been recognised as an official war grave by the Ministry of Defence.
More than 200 men, returning home after the end of World War One, died when the naval yacht HMY Iolaire sank near Stornoway, Lewis, on 1 January 1919.
Western Isles local authority, Comhairle nan Eilean Siar, and SNP MSP Alasdair Allan had campaigned for the legal protection.
Many of the 201 bodies were never recovered.
The war grave recognition prohibits diving of the wreck and the removal of any objects without a UK government-authorised licence.
A national commemorative service was held on New Year's Day this year.
The war grave protection will be in place from 2 September.
Norman Macdonald, chairman of the Iolaire Working Group, said the comhairle welcomed the recognition.
He said: "The comhairle felt that the designation would allow those who perished, to rest in peace, and bring comfort to the many families that lost loved ones."
HMY Iolaire hit a reef called the Beasts of Holm in bad weather close to Stornoway harbour.
Many of the men who died were from the islands of Lewis and Harris.