Area codes 306 and 639 are the telephone area codes in the Canadian province of Saskatchewan, encompassing the province. 306 is the main area code, while 639 is an overlay area code covering the entire province. The incumbent local exchange carrier in 306 and 639 is SaskTel.
The main area code, 306, is one of the original 86 area codes that were assigned in 1947 in the contiguous United States and the then-nine-province extent of Canada. Saskatchewan's second area code, 639, was introduced in 2012, and is an overlay of 306.
In 2012, area code 639 was overlaid onto 306 as a workaround for Canada's inefficient system of number allocation. All competitive local exchange carriers in Canada are allocated exclusive access to at least one three-digit prefix – comprising 10,000 numbers each – for every rate centre where they plan to offer service, even for the smallest hamlets. While each competing carrier does not necessarily need that many numbers in a particular market, unused numbers are unavailable for use elsewhere once assigned to a particular carrier and rate centre. Since number pooling is not used as a relief measure in Canada, this resulted in thousands of wasted numbers. The number shortage was exacerbated by the proliferation of cell phones and other mobile devices requiring unique telephone numbers, particularly in Regina and Saskatoon.
Unlike what was previously done in jurisdictions such as neighbouring Alberta, it was decided to implement the new area code as an overlay rather than a split. Overlays have become the preferred method of area code relief in Canada; no area codes have been split in the country since 1999. While this had the effect of allocating 15.8 million numbers to a province of just over a million people, SaskTel and other carriers wanted to spare existing subscribers, particularly in rural areas, the burden and expense of changing their numbers. 10-digit-dialing began in 2012, and became mandatory throughout the province in May 2013. Until the implementation of 639, Saskatchewan was the last of Canada's original NPAs where seven-digit dialling had not been broken.