UP to 450 new trains could be replaced as part of Northern Trains' 'largest ever' fleet investment.
The publicly owned operator has begun negotiations with train manufacturers to replace the oldest units in its existing fleet.
Most of these have been in service since the 1980s and 90s.
It aims to replace approximately two-thirds of its fleet over the next decade, with a mix of electric and multi-modal (diesel/electric) units.
Manufacturers have also been asked to include battery-powered trains in their proposals.
The multi-modal units will be designed for potential conversion to battery or electric-only operation during their lifespan, aligning with the government's net-zero goals.
Northern Trains believes this will 'significantly simplify' operations, assist with staff training, and reduce maintenance costs, reducing taxpayer subsidy.
Tricia Williams, managing director of Northern, said: "Almost 60 per cent of the trains in our fleet are between 32 and 40 years old and, while they've served the region well, it's important we get the ball rolling on their replacement.
She added: "It also cements electric and battery as the long-term power source of choice for our fleet."
The contract is expected to be awarded in 2026, with the first trains delivered to Northern by 2030.
Lord Hendy, rail minister said: "This vital fleet upgrade will create smoother journeys and help Northern provide the services their passengers deserve.
The first phase of the replacement will target Northern's Class 150, 155, and 156 trains.
It will also include 12 electric three-carriage trains to operate stopping services between York, Leeds, Huddersfield, and Manchester.
This will follow the electrification of the route through the Transpennine Route Upgrade.
Future phases will aim to replace the next oldest fleets as more new trains are produced.
Ms Williams added: "The new trains will support the government's commitment to achieving net zero operations by 2050 whilst reflecting the reality that only 25 per cent of the Northern network is currently electrified."
The train manufacturers approached as part of this first 'Invitation to Negotiate' step in the procurement process are Alstom, CAF, Hitachi, Siemens, and Stadler.
The timelines for introducing the trains will be determined during the procurement process.