LOS ANGELES — A toned and sunburned 32-year-old Australian with the letters F-A-I-T-H tattooed onto his biceps strode onto the stage of a former burlesque theater here and shouted across a sea of upstretched hands and uplifted smartphones: “Let’s win this city together!”

The crowd did not need much urging. Young, diverse and devoted to Jesus, the listeners had come to the Belasco Theater from around the city, and from across the country, eager to help an Australian Pentecostal megachurch that is spreading worldwide establish its first outpost on America’s West Coast.

The church, Hillsong, has become a phenomenon, capitalizing on, and in some cases shaping, trends not only in evangelicalism but also in Christian youth culture. Its success would be rare enough at a time when religion is struggling in a secularizing Europe and North America. But Hillsong is even more remarkable because its target is young Christians in big cities, where faith seems out of fashion but where its services are packing them in.

Powered by a thriving, and lucrative, recording label that dominates Christian contemporary music, it has a vast reach — by some estimates, 100,000 people in the pews each weekend, 10 million followers on social media, 16 million albums sold, with its songs popping up in churches from Uzbekistan to Papua New Guinea.