The 35-year-old musician, who used to date Radio 1 DJ Fearne Cotton, has been charged with conspiracy to engage in sexual activity with a female under 13 and possession or distribution of indecent images of children.
Ian will appear before magistrates in Cardiff, Wales, later today.
A spokesperson for the police said: "A Pontypridd man has been charged with sexual offences against children and is due to appear at Cardiff Magistrates' Court today.
"In order to assist their investigation, South Wales Police has named the man as Ian Watkins, a member of the rock group Lostprophets."
Senior investigating officer Detective Inspector Peter Doyle told the BBC: "Specially-trained staff are available to speak to anyone with concerns or information regarding this investigation and a dedicated telephone number has been set up.
"I want to encourage anyone who has any concerns or information which they think may be relevant to contact us.
"Safeguarding children involved in such cases is always a high priority and as such measures have already been taken."
Alongside Ian two women aged 20 and 24 have been charged with similar offences.
Ian started 'Last Train Home' rockers Lostprophets alongside bassist Mike Lewis, drummer Mike Chiplin and guitarist Lee Gaze in Pontypridd, Wales, in 1997.
The band have sold over 3.5 million albums worldwide, releasing their last, 'Weapons', in April.