Something is changing in an otherwise quiet corner of Christianity in the United States, one that prides itself on how little it has changed over time. Priests are swapping stories about record attendance numbers. Older members are adjusting — or not — to the influx of new attendees. Parishes are strategizing about how to accommodate more prospective converts than existing clergy can reasonably handle on their own.

Across the country, the ancient tradition of Orthodox Christianity is attracting energetic new adherents, especially among conservative young men. They are drawn to what they describe as a more demanding, even difficult, practice of Christianity. Echoing some of the rhetoric of the so-called manosphere, new waves of young converts say Orthodoxy offers them hard truths and affirms their masculinity.

“In the whole history of the Orthodox Church in America, this has never been seen,” the Very Rev. Andrew Damick, an Antiochian Orthodox priest and author in Eastern Pennsylvania, said of the large groups of young people showing up at many parishes. “This is new ground for everyone.”

In the United States, Orthodox Christianity is by far the smallest and least-known of the three major branches of Christianity, representing about 1 percent of the population, compared with about 40 percent who are Protestant and 20 percent who are Catholic. Orthodox pews here have historically been occupied by immigrants from Ukraine, Greece and other countries with large Orthodox populations. Their American-born children often drift to other churches.

But a homegrown Orthodox Christianity is strikingly emergent. Many of the young Americans new to the pews have been introduced to Orthodoxy by hard-edge influencers on YouTube and other social media platforms. Critics call the enthusiastic young converts “Orthobros.”