The Mexican people are expected to write history today by choosing their first female president.
The election campaign has been marked by violence, and just hours before the polling stations opened, a local candidate was killed.
Israel Delgado, 35, was shot near his home in western Mexico on Saturday evening, according to authorities in the state.
More than 25 candidates have been killed during the election campaign.
Polling stations opened at 8 local time, and before the election, the ruling party's presidential candidate Claudia Sheinbaum has had a lead over the main opposition candidate Xóchitl Gálvez.
The only man running, Jorge Álvarez Máynez, has fallen far behind in the polls – which means that a woman is likely to break the highest political glass ceiling in Mexico.
The fight against organized crime is likely to be the biggest challenge. Mexico's organized crime is behind the violent spiral that has claimed the lives of politicians in the country for several years, especially those holding or running for regional and local positions.
Sheinbaum wants to continue on the same line as outgoing President Andrés Manuel López Obrador – with "hugs, not bullets" and social measures to tackle the root of the problem. Gálvez has promised a tougher stance on cartel-related violence.