Third federal electoral district of Sonora

The third federal electoral district of Sonora (Distrito electoral federal 03 de Sonora) is one of the 300 electoral districts into which Mexico is divided for elections to the federal Chamber of Deputies and one of seven such districts in the state of Sonora.

It elects one deputy to the lower house of Congress for each three-year legislative period, by means of the first past the post system. Votes cast in this district also count towards the calculation of proportional representation ("plurinominal") deputies elected from the first region.

District territory
Under the 2022 districting plan, which will be used for the 2024, 2027 and 2030 federal elections, Sonora's third district covers the north-western half of the municipality of Hermosillo, including Tiburón Island. The district's head town (cabecera distrital), where results from individual polling stations are gathered together and collated, is the state capital, the city of Hermosillo.

Previous districting schemes
Between 2017 and 2022, the district had the same configuration as at present.
 * 2017–2022

Under the 2005 plan, the district covered a north-western portion of the municipality of Hermosillo, with its head town in the state capital.
 * 2005–2017

Under the 1996 districting plan, the head town was moved to Hermosillo.
 * 1996–2005

The districting scheme in force from 1978 to 1996 was the result of the 1977 electoral reforms, which increased the number of single-member seats in the Chamber of Deputies from 196 to 300. Under that plan, Sonora's seat allocation rose from four to seven. The third district had its head town at Guaymas and it covered the municipalities of Bácum, Guaymas and Empalme.
 * 1978–1996