The Avelia Liberty is a variant of Alstom's high speed train family that was designed to replace the old Acela Express trains which are in service on the Northeast Corridor between Washington, D.C. and Boston. 28 sets were ordered in 2016 as a replacement for the 20 Acela sets to allow for a tighter schedule. They are being built in the USA with suppliers spread across several states. Introduction into service was initially planned for 2022, but there were several delays after test runs started in 2020. Finally, the first commercial service took place on August 28, 2025.

Each set consists of two 3,500 kW power cars and nine trailers, but there are already provisions for three additional trailers if needed. For certification in the USA, the power cars had to be modified to comply with American crashworthiness standards. In contrast to the Avelia Horizon that is being used in France for TGV services, the trailers of the Avelia Liberty have only one deck, but a tilting mechanism. Although the design speed of these trains was up to 220 mph or 354 km/h, the Northeast Corridor actually only supports much lower speeds. Several stretches of the route have been upgraded from 150 mph to 160 mph (257 km/h) and the trains were also approved for this speed. In reality, the average speed is around 70 mph.