Ariana Grande is spreading a little extra love in the Big Apple … teaming up with boyfriend Ricky Alvarez to give one New York City Marathon runner the surprise of a lifetime.

The couple was spotted cheering on runners from the sidelines Sunday when an influencer named Ella Schweiger approached them with an unusual request … write a message of encouragement for a complete stranger who had just tackled the grueling 26.2-mile race.

Ariana was more than happy to oblige … grabbing a pen and writing “You did it!” alongside some hearts. She signed the sweet note, “Ari + Ricky.”

Ella shared video of the encounter on Instagram … showing the moment she approached the couple before delivering the message to a runner named Ellie, who was absolutely floored to learn who had written it.

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And get this … Ellie revealed she’d actually been listening to Ariana’s music during the race, saying one of her songs helped push her through a particularly brutal stretch around mile 24.

The whole thing was part of Ella’s project, “Ella’s Envelope,” which collects uplifting messages from strangers and delivers them to runners … proving a few kind words can go a long way.

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As for Ariana and Ricky … the two rekindled their romance earlier this year, nearly a decade after their first breakup, and made things Instagram official in August.

The race may have been 26.2 miles … but Ari’s kindness went even further.

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