China's ruling Communist Party has decided to allow all couples to have two children, abolishing a policy that limited many urban couples to only one child for more than three decades.
The decision is the most significant easing of family planning policies that were long considered some of the party's most onerous intrusions into family life.
The restrictions led to an imbalanced sex ratio because of a traditional preference for boys, and a strict enforcement that sometimes included forced abortions.
A communique from the party's Central Committee said that the decision to allow all couples to have two children was "to improve the balanced development of population" and to deal with an ageing population, the official Xinhua News Agency said.
However, the move may not spur a huge baby boom, in part because fertility rates are believed to be declining even without the policy's enforcement.
Previous easings of the one-child policy have led to fewer births than expected, and many people among China's younger generations seem to prefer smaller family sizes.
The communique followed the panel's meeting this week to chart the country's economic and social development to 2020.
It is unusual for such plenary sessions to result in major decisions, and there was no indication that this one would take action on the one-child policy.
China, which has the world's largest population at 1.4 billion people, introduced the one-child policy in 1979 as a temporary measure to curb a then-surging population and limit the demands for water and other resources.
Soon after it was implemented, rural couples were allowed two children if their firstborn was a girl. Ethnic minorities are also allowed more than one child.
Chinese families with a strong preference for boys have sometimes resorted to aborting female foetuses, a practice which has upset the ratio of male to female babies.
The imbalance makes it difficult for some men to find wives, and is believed to fuel the trafficking of women as brides.
Couples who broke the rules were forced to pay a fee in proportion to their income. In some cases, rural families saw their livelihood in the form of their pigs and chickens taken away.
In November 2013, the party announced that it would allow couples to have two children if one of the parents is a single child.
The decision announced on Thursday removes all remaining restrictions limiting couples to only one child.
The government credits the one-child policy with preventing 400 million births and helping lift countless families out of poverty by easing the strain on the country's limited resources.
But many demographers argue the birthrate would have fallen anyway as China's economy developed and education levels rose.
Moreover, the abrupt fall in the birthrate has pushed up the average age of the population and demographers foresee a looming crisis because the policy reduced the young labour pool that must support the large baby boom generation as it retires.
Cai Yong, a sociology professor at the University of North Carolina at Chapel Hill, said: "The good news is, it is here. The bad news is, it is too little too late."
Willy Lam, an expert on Chinese politics at the Chinese University of Hong Kong, said: "It's better late than never.
"It might serve to address the current imbalance in the sense that if they do not boost the growth rate then very soon, within 20 years or less, the working population will be supporting four aged parents."