No app was going to save this thief.

Two good Samaritans chased down and tackled an iPhone crook yesterday after the thief snatched the device out of a woman’s hand as she surfed the ’Net outside her lower Manhattan office, police said.

“I couldn’t believe it, complete strangers helping,” said Erika Silva, 23. “I’m glad so many people helped me.”

Amateur crime fighters Brian Hester (inset) and Alvern Bunn were on a smoke break at around 11:30 a.m. when Noah Udell, 26, allegedly blindsided Silva outside 100 Church St.

“I was surfing through the Internet, and this guy just snatched it,” she said.

Bunn and Hester saw the woman briefly chase the crook and struggle for her phone.

“She was screaming, ‘Help!’ ” Hester told The Post. “They were wrestling. He snatched the phone and pushed her.”

Hester — who sells office space when he’s not battling bad guys — sprung into action.

“I just ran,” he said. “My coffee went everywhere, and my phone fell out of my pocket.”

Bunn (pictured above, far right) was the first to grab Udell, 26, but hurt his knee in the attempted citizen’s arrest. Hester then knocked the suspect to the ground but got slightly dazed himself in the fall.

That’s when a crowd of other outraged bystanders started to gather, and one man stomped his foot onto Udell’s throat.

Hester said he actually had to hold off angry onlookers. In the process, Udell jumped up and once again bolted.

Hester chased him a second time, catching him on Barclay Street near West Broadway.

“I was like, ‘I don’t have all day to be chasing you,’ ” Hester said he told Udell.

Hester then held Udell until cops arrived. “Thieves need to know, ‘You’re not going to get away with this in broad daylight,’ ” Hester, of Wayne NJ, said.

Udell, of Queens, has been charged with second-degree robbery and assault.

Silva, who works in billing at a health-care company, said she was happy Udell didn’t steal her phone because it contains pictures of her 3-year-old son.

“He chose the wrong woman on the wrong day,” she said.

While being a hero is its own reward, Hester also got a more practical reward for his actions.

“Starbucks gave me a free refill on my coffee,” he said.