President Biden is starting his week off with a wedding ... because his nephew is about to tie the knot with a real housewife.

The White House says the President and First Lady Jill Biden will be in attendance when Biden's nephew, Cuffe Owens, marries 'Real Housewives of Orange County' star Meghan O'Toole King today.

Monday's ceremony is said to be pretty small and reserved for family ... and it's going down at the home of Biden's sister, Valerie Owens.

Cuffe is a 42-year-old attorney based in Los Angeles, and he only recently went public with his relationship with Meghan.

It's the third marriage for Meghan ... remember, her last marriage to former MLB star Jim Edmonds ended in a messy divorce complete with a nude text messaging scandal and alleged infidelity with their nanny.

POTUS is attending the wedding after spending the weekend back home in Delaware, then it's back to The White House.

No word if Biden's planning to say a few words at the ceremony.