Mytravelpass, which is funded by the Welsh government, will entitle 110,000 passengers aged 16-18 to a third off bus fares anywhere in Wales.
Transport Minister Edwina Hart said it would make it easier for young people to access jobs and training opportunities.
The pass applies to local journeys and longer distance TrawsCymru routes.
The scheme is part of a Labour-Liberal Democrat deal struck in September 2014 to pass the Welsh government's budget.
A £15m discounted bus travel scheme for young people has been launched.