First Minister Nicola Sturgeon will officially open the new Museum nan Eilean at Lews Castle on Monday March 6.
A spokesperson for the museum said: "We are delighted that Nicola Sturgeon has agreed to open the new museum. It's all come about a bit suddenly because of a space becoming available in her diary, but we very much look forward to welcoming her."
The new Museum nan Eilean at Lews Castle offers an interactive explanation of the history and culture of the Outer Hebrides alongside a stunning exhibition of unique objects dating from prehistory to the present day.
The museum introduces life in the Outer Hebrides from prehistory to the present day with a range of Gaelic-led exhibitions including significant archaeological finds from National Museum Scotland.
Six of the famous Lewis Chessmen have returned to the island of their 1831 discovery from the British Museum and take their place as centrepiece exhibits.
Visitors can hear residents of the islands talk about their unique lifestyle and culture, and take a journey across the islands in a series of dramatic videos covering landscapes from the north of Lewis all the way to Barra, filmed day and night throughout the year.