Bannan will be produced by Christopher Young, the man behind The Inbetweeners, and is being shot on Skye. It is being written by Chrisella Ross, and directed by Tony Kearney.
It is BBC Alba's most ambitious move yet and the channel hopes there will be an international market for Bannan, which Mr Young, who has lived on Skye for 15 years and speaks Gaelic, has compared in tone to dramas such as Breaking Bad or Friday Night Lights, adding that the success of subtitled dramas such as The Killing show there is an appetite for quality drama of any language.
Three half-hour pilot episodes, in Gaelic with English subtitles, will be recorded and shown on BBC Alba next year, and it is hoped that around 15 more episodes will follow, appealing strongly to a young and female audience.
Although it is being shot in Skye, Bannan is set on a imaginary island.
The project has received £300,000 funding from Creative Scotland, and is the most expensive project yet for the five-year-old channel, which attracts 600,000 viewers a week.
Bannan, which means roughly the 'ties that bind', follows Mairi Macdonald and her return to the island she left eight years ago at the age of 18.
Mr Young, who made Gaelic film, Seachd: The Inaccessible Pinnacle, in 2007, said: "We are shooting very high-end, on location not on sets, so in terms of tone, it is somewhere between the American dramas and the Danes - it is about quality and character.
"We are very keen to do something that is contemporary, we want to bring a drama in Gaelic firmly to a 21st century audience, we want to talk about 21st century Gaels.
"We are very keen that we are talking about real Gaels, not a fantasy or Monarch of the Glen, and once we have got a loyal following, and people have taken them into their lives, we can push them into some quite dangerous places."
Cast members, who all speak Gaelic, include Debbie Mackay, Peigi Wood, Daibhidh Walker, Kathleen MacInnes, Dòmhnall Eoin MacFhionghain and Iain MacRae.
Mr Young added: "We are making the best of the funding. I am aware that we are making something for BBC Alba and it is a big investment for them.
"But in television terms it is for half the cost of the average BBC drama, and we have to bear that in mind, because we will be judged absolutely by those standards."
Margaret Mary Murray, BBC Alba's head of service, said: "We are proud to be delivering another strong package of programmes for our autumn schedule. Bannan is a fantastic step forward for BBC Alba."