Yoko Ono -- Rushed To Hospital ... Where John Lennon Died

9:52 P.M. PST -- Ono's son Sean just tweeted, "Hey guys it was only rumors from press: was NOT a stroke, just dehydration/tired. She is FINE. Thank you everyone for your concern."

Yoko Ono was rushed to a NYC hospital Friday after falling ill ... and she was taken to the same NYC hospital where her husband John Lennon died more than 3 decades ago.

Media reports started to swirl she had a stroke but her rep quickly walked that back.

Ono's rep tells TMZ the 83-year-old began to feel sick and called her doctor. Her doc urged her to get to the hospital to get checked out so she called for an ambulance.