The 21st federal electoral district of the State of Mexico (Spanish: Distrito electoral federal 21 del Estado de México) is one of the 300 electoral districts into which Mexico is divided for elections to the federal Chamber of Deputies and one of 40 such districts in the State of Mexico.^[1]

It elects one deputy to the lower house of Congress for each three-year legislative session by means of the first-past-the-post system. Votes cast in the district also count towards the calculation of proportional representation ("plurinominal") deputies elected from the fifth region.^[2][3]

The 21st district was created by the 1977 electoral reforms, which increased the number of single-member seats in the Chamber of Deputies from 196 to 300. Under that plan, the State of Mexico's seat allocation rose from 15 to 34.^[4] The new districts were first contended in the 1979 mid-term election.

Under the National Electoral Institute's 2022 districting plan, which is to be used for the 2024, 2027 and 2030 federal elections,^[5] the 21st district is located in the state's eastern panhandle and covers 12 of its 125 municipalities:

• Amecameca, Atlautla, Ayapango, Cocotitlán, Ecatzingo, Juchitepec, Ozumba, Temamatla, Tenango del Aire, Tepetlixpa, Tlamanalco and the eastern portion of Ixtapaluca.^[6][7][a]

The district's head town (cabecera distrital), where results from individual polling stations are gathered together and tallied, is the city of Amecameca de Juárez. In the 2020 Census, the district reported a total population of 410,835.^[1][8]

Under the previous districting plans enacted by the INE and its predecessors, the 21st district was situated as follows:

2017–2022

Ten municipalities in the eastern panhandle: Amecameca, Atlautla, Ayapango, Ecatzingo, Juchitepec, Ozumba, Tenango del Aire, Tepetlixpa, Tlamanalco and the eastern portion of Ixtapaluca. The head town was at Amecameca de Juárez.^[10][11]

2005–2017

A portion of the municipality of Naucalpan de Juárez.^[9][12]

1996–2005

The northern, north-eastern and western parts of Naucalpan de Juárez.^[9]

1978–1996

The municipalities of Acolman, Apaxco, Axapusco, Hueypoxtla, Jaltenco, Melchor Ocampo, Nextlalpan, Nopaltepec, San Martín de las Pirámides, Tecámac, Temascalapa, Teoloyucan, Teotihuacán, Tequixquiac, Tezoyuca, Tultepec and Zumpango, with its head town at Zumpango de Ocampo.^[13]

National parties
Current
	PAN
	PRI
	PT
	PVEM
	MC
	Morena
Defunct or local only
	PLM
	PNR
	PRM
	PP
	PPS
	PARM
	PFCRN
	Convergencia
	PANAL
	PSD
	PES
	PRD

Twenty-first federal electoral district of the State of Mexico

Election	Deputy	Party	Term	Legislature
1979	Alfredo Navarrete Romero[14]		1979–1982	51st Congress
1982	Hugo Díaz Thomé[15]		1982–1985	52nd Congress
1985	Pedro Zamora Ortiz[16]		1985–1988	53rd Congress
1988	Cecilio Barrera Reyes[17]		1988–1991	54th Congress
1991	Javier Barrios González[18]		1991–1994	55th Congress
1994	Leonel Domínguez Rivero[19]		1994–1997	56th Congress
1997	Héctor Flavio Valdez García[20]		1997–2000	57th Congress
2000	Moisés Alcalde Virgen[21]		2000–2003	58th Congress
2003	Manuel Gómez Morín Martínez del Río[22]		2003–2006	59th Congress
2006	Edgar Olvera Higuera[23] María Eugenia Patiño Sánchez[24][b]		2006–2009 2009	60th Congress
2009	Rodrigo Reina Liceaga[25]		2009–2012	61st Congress
2012	Cristina Ruiz Sandoval[26]		2012–2015	62nd Congress
2015	Luis Gilberto Marrón Agustín[27] Jaime Mauricio Rojas Silva[28][c]		2015–2018 2018	63rd Congress
2018	Graciela Sánchez Ortiz[29]		2018–2021	64th Congress
2021	Graciela Sánchez Ortiz[30]		2021–2024	65th Congress
2024[31]	Iván Millán Contreras[32]		2024–2027	66th Congress

19°45′N 99°10′W / 19.750°N 99.167°W / 19.750; -99.167