NAYPYITAW, Myanmar — For a generation and more, they were the persistent, often persecuted opposition. On Monday, Aung San Suu Kyi’s prodemocracy party took a momentous step toward becoming Myanmar’s government.

Led for the first time by the National League for Democracy, parliament began a heady and historic session that will install the country’s first democratically elected government in more than 50 years.

The NLD won a landslide victory in Nov. 8 elections, taking about 80 percent of the seats at stake in the two houses of parliament to defeat the military-backed Union Solidarity and Development Party.

Many legislators expressed hope that it was the beginning of a new, brighter era following decades of military oppression, civil war, and pervasive poverty.

‘‘This is like a dream for me,’’ Khin Maung Myint, an NLD lawmaker, said before the ceremonial two-hour session. ‘‘I never imagined that our party would be able to form the government. Even the public didn’t think we could have an NLD government. But now it is like a shock to us and to the world too.’’ 

 Legislators from the two main parties, smaller ethnic minority parties, and military-appointed representatives filed into the cavernous parliament for the lower house session and took a joint oath of office.

 Most wore the traditional dress of the Burman majority or of the Shan, Karen, Kachin, Lisu, and other minorities who make up nearly 40 percent of the country’s 52 million people but have been poorly represented in the government in the past.

 The session marks a historic turnaround for the NLD, which for years was suppressed by the military. Generals ruled the country directly or indirectly after seizing power in 1962, and over the years jailed hundreds of NLD leaders, including Suu Kyi, while crushing overt political activity.

 The Southeast Asian nation started moving away from dictatorship toward democracy in 2011, when the military rulers agreed to hand over power to a nominally civilian government headed by President Thein Sein, a general-turned-reformist.

He will step down in late March or early April when an NLD president takes over.

Suu Kyi is constitutionally barred from taking the presidency because her late husband and sons are British, and has vowed to rule from behind the scenes through a proxy. She has not announced who her party will nominate for president.

 After two meetings between Suu Kyi and armed forces commander General Min Aung Hlaing, rumors surfaced that she was pressing for the suspension of the constitutional clause that bars her from office.

 But the speculation was quashed Monday by the army’s Myawaddy Daily newspaper, which wrote that ‘‘for the goodness of the mother country’’ the constitutional clause should not be changed.

 Despite its landslide victory, the NLD will have to share power with the military because the constitution reserves 25 percent, or 166 of the 664 seats in the two houses of parliament, for military appointees.