The Mombasa–Nairobi Standard Gauge Railway, completed in 2017, was built as the first phase of the Kenya Standard Gauge Railway. It is a standard-gauge railway (SGR) in Kenya that connects the large Indian Ocean city of Mombasa with Nairobi, the country's capital and largest city. This SGR runs parallel to the narrow-gauge Uganda Railway that was completed in 1901 under British colonial rule. The East African Railway Master Plan provides for the Mombasa–Nairobi SGR to link with other SGRs being built in the East African Community.

Mombasa is a coastal city in southeastern Kenya along the Indian Ocean. It was the first capital of British East Africa, before Nairobi was elevated to capital status in 1907. It now serves as the capital of Mombasa County. The town is known as "the white and blue city" in Kenya. It is the country's oldest and second-largest city after Nairobi, with a population of about 1,208,333 people according to the 2019 census. Its metropolitan region is the second-largest in the country, and has a population of 3,528,940 people.