David Del Rio has brought in one of Hollywood’s most powerful attorneys — Shawn Holley — in the wake of his sudden firing from CBS’ “Matlock” after his costar Leah Lewis accused him of sexual assault … TMZ has learned.

Sources with direct knowledge tell TMZ … Del Rio retained Holley — whose client list includes the likes of Kim Kardashian, Justin Bieber, and Lindsay Lohan — this week as he navigates the fallout from the allegation that got him booted from the hit CBS show last month.

TMZ broke the story … Leah filed an allegation with CBS against David on Oct. 2 for an alleged sex assault she claims occurred Sept. 26. We were told on the day of the report, he was removed from the lot … and after an investigation, he was fired. CBS Studios confirmed his character, a lead in the series, will be written off.

The LAPD told us at the time there was no record of an assault report matching the date or location of Lewis’ allegation.

Shortly after news broke, Leah posted a message to fans alongside a photo hugging her mom, writing … “Mom is here, we’re moving forward in love and strength. I’m in good hands. Thank you to everybody for any kind of support and care. Truly, we’re moving forward in strength. Key word, strength.”

David’s wife, Katherine Del Rio, also sounded off … blasting Leah as “the most disturbing human being I have ever met.”

We reached out to Holley and Del Rio for comment … so far, no word back.