The Monumental Axis (Portuguese: Eixo Monumental) is the central and main avenue in Brasília's city design. The avenue begins on the National Congress of Brazil building and is considered part of the DF-002 road. Its first section is known as "Ministries Esplanade" ("Esplanada dos Ministérios"), as it is surrounded by ministries buildings. Many important government buildings, monuments and memorials are located on the Monumental Axis.

It is 16 kilometers long, beginning at the Rodoferroviária de Brasília, and ending at the Praça dos Três Poderes. It was created by Lúcio Costa during the construction of Brasília's Plano Piloto, connecting with the Highway Axis (Portuguese: Eixo Rodoviário) at the Pilot Plan Bus Station.

A common urban legend persists that the Monumental Axis is the widest road in the world, where "[100 to 160] cars can drive side by side". This is untrue, as the road consists of two avenues with six lanes on either side; a total of twelve lanes. However, the street has been featured in the Guinness Book of Records as having the widest median strip of a highway in the world. On April 21, 2008, a year before they formally broke up, the Mexican pop group RBD performed a free concert to a crowd of 500,000 on the Monumental Axis during Empezar Desde Cero Tour 2008. The show was to celebrate the 48th Anniversary of the founding of Brasília. It was recorded and released on DVD with the title Live in Brasilia. The crowd in attendance was the largest for which the group had performed.