Lady Gaga gave some great insight as a judge on "So You Think You Can Dance" last night -- but one contestant almost left her speechless.

After Marko performed a powerful Sonya Tayeh contemporary with Allison, Gaga couldn't help but give them a standing ovation ... and then the tears started.

"I'm just so proud of you" she said, before stopping to compose herself. "You know, you really love to dance are absolutely incredible."

Marko was overcome with emotion too, and with good reason: His mom flew in from Guam to watch his performance.

See the dance that made Gaga cry above!

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