Network Rail said the revamp has led to a bigger, better and brighter station with a new, second concourse and airport entrance, which has doubled the space for the millions of passengers that use the station each year.
The first passengers to use the new concourse and airport entrance arrived on the 05.48 Thameslink Bedford to Brighton service on platform 7.
The revamp includes eight new escalators and five new lifts. The new lifts and escalators, along with four new stairways and widened platforms, will help passengers move between the train station and the airport more quickly and easily, Network Rail said.
It added that easier journeys from train to plane will benefit passengers across the wider network, helping keep trains running on time by removing the congestion and queuing on platforms that delay trains.
It said passengers travelling on the Brighton Main Line are already seeing the benefits of the project, thanks to track upgrades which Network Rail said have helped reduce journey times between Brighton and London to one hour on some services.
The existing station concourse is also bigger with new customer information systems, more ticket gates, and a dedicated passenger assistance point.
The new concourse will now act as the new entrance for people accessing the airport terminal, while the existing concourse will be for people exiting.
The existing station concourse, station footbridges and the South Terminal linkspan have been refurbished and reconfigured to provide a seamless one-way system to the airport from the train station, Network Rail said.
Lucy McAuliffe, Network Rail Sussex route director, said: “I’m delighted to see the upgraded Gatwick Airport station open today, providing the millions of passengers that use the station each year with a fantastic and fit-for-purpose station that supports the ambitions of London Gatwick and the significant growth in passengers expected in the years to come.
“This has been a highly complex and challenging project and I am proud of how hard our teams have worked in close conjunction with our partners to deliver a station upgrade that makes journeys to the airport much easier for all passengers and encourages people to ditch the car and travel by rail, the cleanest and greenest way to travel.
“This project is not just for those making their way to the airport, the work benefits passengers right across the route by giving them quicker journeys and a more reliable timetable. I hope passengers enjoy this newly upgraded station.”
Transport Secretary, Mark Harper, said: “With millions of people travelling into Gatwick Airport by train each year, this station is a major public transport hub and has been upgraded thanks to Government funding, improving the train-to-plane journey and delivering more reliable services for passengers.
“Today’s opening demonstrates this Government’s commitment to funding improvements to our rail network, transforming a vital station into an impressive gateway to the UK and helping more British and international passengers to travel by train.”
Jenny Saunders, customer services director for Govia Thameslink Railway, said: “Our trains sustainably speed people to the airport in just half an hour from London - and that's much better for the environment than driving.
“However, the station has been struggling with the numbers using it and that holds up our trains, delaying everyone.
“This stunning redevelopment has fixed all that. I genuinely believe our customers are going to love the extra space and improved accessibility that will make the journey between train and plane quicker, easier and more attractive."
Jonathan Pollard, chief commercial officer, London Gatwick, said: “From today, airport passengers travelling by train will have a dramatically improved experience as they pass through the bigger, better and brighter new station concourse. This fantastic new, fully accessible station concourse will encourage even more passengers to come to the airport using sustainable public transport.”