Sky Mobile will offer flexible monthly payment plans and the ability to roll over unused data each month for up to three years.
Sky will become a "quad play" provider, offering broadband, television fixed-line telephone and a mobile service.
And existing Sky TV customers will not have to pay for calls or texts and can compile playlists of their favourite shows to watch on their mobiles.
According to Sky, some 46,000 have pre-registered for the service.
The service comes with three data plans:
Non-Sky TV customers can add on unlimited calls and texts for £10 per month, or pay for calls and texts on a pay-as-you-use (PAYU) basis.
According to Sky, UK consumers use less than half of the mobile data they buy from mobile network operators, adding up to an annual £2bn of wasted data.
Stephen van Rooyen, UK and Ireland Sky chief executive, said:  "We felt it was time to shake up the mobile market and give customers a completely new way to manage their mobile plan.
"We've designed it based on what people told us they want - it's easy, flexible and transparent and it puts the customer in control."
Ewan Taylor-Gibson, a telecoms expert at uSwitch said: "Sky's first mobile offering is very competitive, as long as you're already a Sky TV customer."
He compared Sky's Sim-only deal with that already offered by giffgaff, another service that piggybacks on O2's network and allows customers to alter their package depending on their usage.
"The key differences between the two are that Sky ties you in for 12 months, while giffgaff users can cancel anytime, and giffgaff also offers unlimited everything for £20 a month, beating Sky's top package, which delivers 5GB," said Mr Taylor-Gibson.
Sky's decision to let people roll over data and store it for three years was "both unique and compelling", he said, but it may have to offer bigger data bundles.
Broadcaster Sky is launching its own mobile phone service.