The Panama Canal expansion referendum was held on October 22, 2006, when the citizens of Panama approved the Panama Canal expansion project by a wide margin.

The Panama Canal expansion project (Spanish: ampliación del Canal de Panamá), also called the Third Set of Locks Project, doubled the capacity of the Panama Canal by adding a new lane of traffic allowing for a larger number of ships, and increasing the width and depth of the lanes and locks allowing larger ships to pass. The new ships, called New Panamax, are about one and a half times the previous Panamax size and can carry over twice as much cargo. The expanded canal began commercial operation on 26 June 2016.

The project has:

Built two new sets of locks, one each on the Atlantic and Pacific sides, and excavated new channels to the new locks.

Widened and deepened existing channels.

Raised the maximum operating water level of Gatun Lake.Then-Panamanian President Martín Torrijos formally proposed the project on 24 April 2006, saying it would transform Panama into a First World country. A national referendum approved the proposal by a 76.8 percent majority on 22 October, and the Cabinet and National Assembly followed suit. The project formally began in 2007.

It was initially announced that the Canal expansion would be completed by August 2014 to coincide with the 100th anniversary of the opening of the Panama Canal, but various setbacks, including strikes and disputes with the construction consortium over cost overruns, pushed the completion date back several times. Following additional difficulties including seepage from the new locks, the expansion was opened on 26 June 2016. The expansion doubled the Canal’s capacity. On March 2, 2018, the Panama Canal Authority announced that 3,000 New Panamax ships had crossed the canal expansion during its first 20 months of operation.