For decades, social scientists, demographers and Christians themselves have told a familiar story about the state of Christianity in the United States: The country was rapidly secularizing. The Christian population was shrinking, on its way to becoming a minority religion. America may have been some years behind Europe in the process, but its pews were emptying steadily and inexorably.

Now, that narrative may be changing.

After years of decline, the Christian population in the United States has been stable for several years, a shift fueled in part by young adults, according to a major new survey from the Pew Research Center. And the number of religiously unaffiliated Americans, which had grown steadily for years, has also leveled off.

“We’re entering a new era of the American religious landscape,” said Ryan Burge, a political scientist at Eastern Illinois University who was not involved in the Pew survey. The “nones” — those in the American population who tell researchers they have no religious affiliation — have been growing for decades. “Now that growth has either slowed or stopped completely,” Dr. Burge said, “and that’s big deal.”

The findings come from the Religious Landscape Survey, a survey of more than 35,000 randomly selected adults from across the country conducted in 2023 and 2024. The last survey was published in 2014, making the new edition’s release a major update in the understanding of American spiritual beliefs and practice.

The survey finds that 62 percent of adults in the United States describe themselves as Christians, including 40 percent who identify as Protestant and 19 percent who are Catholic.

Overall, that represents a decline in the share of Christians since the survey was first published in 2007. As recently as the early 1990s, nine in 10 adults in the country identified as Christian. Almost 30 percent of adults participating in the new survey are religiously unaffiliated, and 7 percent identify with a religion other than Christianity.

“If you look to the long term, it’s a story of decline in American religion,” said Gregory Smith, a senior associate director of research at Pew. “But it’s a completely different story if you look at the short term, which is a story of stability over the last four or five years.”

The story of the steadying is complex, but one factor is the youngest cohort of adults in the survey. The survey’s first two editions have shown each age group becoming steadily less Christian than the previous. For example, 80 percent of those born in the 1940s or earlier now identify as Christian, compared with 75 percent of those born in the 1950s and 73 percent of those born in the 1960s.

People in the youngest age group in the new survey, born between 2000 and 2006, appear to defy that trend. They are still less likely than average to identify as Christian, and far less likely than the oldest Americans. But, intriguingly to researchers, they appear no less religious than survey participants in the second-youngest cohort, born in the 1990s.

The youngest survey participants stood out in other ways, too. The gap in religiosity between men and women is far smaller than it is in older generations. Typically, women are more religious than men on a variety of measures. It’s a pattern so consistent across time, geography and culture that some scholars characterize it as a fact of human life. The pattern shows up in Pew’s oldest cohorts, where, for example, women are 20 points more likely than men to say they pray every day.

Among 18- to 24-year-olds in Pew’s survey, however, the gender gap is small or nonexistent in measures of whether they pray daily, identify with a particular religion and believe in God.

“It’s not quite a reversal, but the fact that it’s narrowing is significant,” said David Campbell, a political scientist at the University of Notre Dame who was not involved with the survey.

Dr. Campbell speculated that the cause of the convergence might be at least partly political. As the perception of Christianity in particular has become increasingly entangled with conservative political movements, identifying as a Christian has become a matter of conservative identity.

“If you’re a young white male these days and you think of yourself as conservative, then being religious is a part of that,” he said.

The survey was conducted before President Trump’s re-election and the subsequent “vibe shift” detected by many religious conservatives, a rightward turn that includes celebrity conversions and a Silicon Valley backlash against progressivism. Still, people who are politically conservative and liberal are on dramatically different trajectories religiously, the Pew survey affirms. The share of self-described liberals who identify as Christian has dropped by 25 points since 2007. Just over a third of liberals now identify as Christian, and more than half say they have no religion.

Among conservatives, the decline in Christian identification has been much more subtle, to 82 percent from 89 percent.

The Census Bureau does not ask questions about religion, so Pew’s large and rigorous survey is a key resource for academics, journalists and the general public. The new survey is the largest of the three that have been conducted so far.

“It’s difficult to overstate the importance” of the survey to the understanding of American religion, Dr. Campbell said.

Researchers caution that the data does not indicate an actual reversal in the decline of Christianity, or even that the plateau will last. Young adults are still significantly less religious than older adults, meaning they will pull down the average religiosity over time. It is unlikely that the current group of young adults will become more religious as they age.

But some experts suggest that most people who were going to leave a religion have done so by now, raising the possibility that the data might offer a hint at the natural ceiling of nonreligiosity in the United States.

“The ‘nones’ have run through the easy parts of the market, and now they’re hitting the bedrock of committed evangelicals” and theological traditionalists in other faiths, said Dr. Burge, who was also pastor of an American Baptist church for 17 years. Going forward, “if you’re going to make advances, you have to make advances with conservatives.”

Regardless of how many Americans identify with specific religions — or no religion at all — in the future, the survey depicts a fundamentally spiritual population. More than 80 percent of survey participants believe humans “have a soul or spirit in addition to their physical body,” and believe in God or a universal spirit.

Most paths to religion are highly personal.

Justin Springhart, 32, began attending Orlando Grace Church in Florida, a nondenominational church, a few years ago after having drifted away from religion. When his brother died of a drug overdose, he found he was so closed off from his own emotions that he couldn’t cry at the funeral.

When his personal trainer invited him to a church service, he felt at home as soon as he walked in the door.

“It just felt like this is where I need to be to grow as a man, to grow in Christ, to grow as a leader,” Mr. Springhart said. “As someone who couldn’t cry at his own brother’s funeral, I weep about how much my God loves me.”