Lionel Richie is hospitalized in the intensive care unit in St. Louis after performing in the city over the weekend … TMZ has learned.

Sources with direct knowledge tell TMZ … Lionel checked himself into a local hospital after his Saturday night performance at The Muny in Forest Park to have some tests run.

We’re told Lionel is being cautious and doctors are looking into possible slight dehydration. Our sources say he’s hoping to be discharged Tuesday.

Witnesses at the concert tell us Lionel appeared to be struggling a bit toward the end of the show, asking his team to bring him a chair while performing his final song, “All Night Long,” so he could sit down.

As we broke the story … Lionel was also rushed to a hospital in June after falling ill onstage during a concert in St. Paul, Minnesota. Lionel told the crowd he felt “dizzy” and “strange” and cut the show short before paramedics met him backstage and took him to a hospital by ambulance.