KeolisAmey has taken over as operator of rail services for Wales and Borders, replacing Arriva Trains Wales, which operated the franchise since 2003.
The franchise will be overseen by Transport for Wales (TfW) and receive an investment of £5bn over the contract period.
The contract is valid for 15 years and TfW is expected to offer 600 jobs and 450 apprenticeships.
Around £800m will be invested to procure new trains, and £194m will be allocated to improve passenger experience at stations across the Wales and Borders network.
Wales First Minister Carwyn Jones said: “Led by Transport for Wales with our partners KeolisAmey, this will be the very first ‘made in Wales’ rail service, designed and delivered by the Welsh Government.
“The opportunity to redesign and repurpose our railway network in Wales is a once in a generation opportunity, and I am confident that by 2033 it can be the best passenger rail service in the UK.”
Welsh Transport Secretary Ken Skates noted that 95% of the existing trains will be replaced by 2023.
Skates said: “There is £738m earmarked to modernise the central metro lines, support the next phase of Metro and run more trains every hour.”
KeolisAmey is a joint venture between French transport company Keolis and infrastructure asset management specialists Amey. It won the contract to operate the Wales and Borders rail service and the South Wales Metro in May.