A Cubs fan tumbled into a basket at Wrigley Field on Monday night in a hunt for a home run ball ... and the wild scene was all captured on video.
It happened in the second inning of Chicago's tilt with the Kansas City Royals ... after Jac Caglianone took a Ben Brown knucklecurve deep to left field.
The ball crash landed into a net at the top of the wall -- giving the star rookie a home run ... but in an effort to retrieve the keepsake, a man in a black tank top and Cubs headband fell head-first into the webbing.