This is a move aimed at improving security after the murder of three foreign aid workers, an official said on Sunday.
"Any foreigner who declines to leave will be charged with illegally staying in Somaliland," Husayn Ali Duale, Somaliland finance minister said.
"The outsiders are a security threat to our nation," he added.
The order follows the 21 October killing of two British teachers, Richard Eyeington and his wife Enid, by unknown gunmen.
Only over two weeks earlier on 5 October, Italian aid worker, Annalena Tonelli, 60, was shot dead in Somaliland.
Authorities have blamed the murders on "foreigners".
Former British protectorate
Somaliland, a former British protectorate, became independent on 26 June 1960, but days later united with the Italian colony in the south to form the republic of Somalia.
It seceded from Somalia in May 1991, five months after late Somali strongman Muhammad Siad Barre was overthrown and has remained relatively calm even as the rest of the country was plunged into anarchy.
"Outsiders are a factor in the destabilisation of Somaliland after 13 years of peace".
Duale added that "the killing of aid workers has forced us to boost security".