Louis Frédéric Grimaldi (formally Prince Louis of Monaco) is the ex-husband of Blair Waldorf and, as a member of the Grimaldi family, a Monégasque prince. He is the son of Princess Sophie of Monaco and older brother of Princess Beatrice. Louis is portrayed by Hugo Becker.
Louis and Blair met at the Musée d'Orsay in Paris at the beginning of season four (Belles de Jour), where Blair is staring at her favorite painting by Manèt. Louis approaches her, and admits he's been trying to work up the courage for awhile to ask her out. He asks her out, although he later tells her he's bringing a friend and Blair in turn invites Serena so they can double date. Blair suspects Louis is royalty and is very excited. During the date, he pretends his friend Jean Michele is the royal one and Blair decides to focus her attention on him. After Serena and Jean Michele leave, he confesses to Blair that he is the royal one and tested her to make sure she wasn't using him, and she failed.
The next day, Blair convinces him to give her another chance. They go on a fun date and are going to go to a ball, but Blair is pulled away to stop Chuck from running away from his life. Their short-lived romance ends when Blair goes back to New York leaving Louis with one of her shoes and says he can always come find her (Double Identity).
Towards the end of season four, Louis arrives in Manhattan with Blair's shoe and they start dating again. He comes secretly, although his cover is almost blown when Dan is assigned to write an article about it. When his family finds out, Blair devises a scheme to pretend Louis is actually there for a charity event (Petty in Pink). During the party, she kisses Dan and Serena tells Louis that Blair has been interested in Dan for awhile. However, the two eventually makeup.
Sophie Grimaldi, Louis' mother, soon arrives in the city and does not approve of Blair as a partner for Louis, as she is not royalty. Also, Serena is still mad at Blair for Dan and gives Sophie a book full of Gossip Girl blasts on Blair's wrongdoings (The Princesses and the Frog). Eventually with the help of Cyrus, Blair is able to win Sophie over (Shattered Bass).
At the end of season four, Louis and Blair get engaged and plan to spend the summer in Monaco together. Blair is also pregnant but miscarries during a car accident in Season Five (Riding in Town Cars With Boys).
The royal wedding is still on, but Blair is frustrated that Louis is unable to stand up to his mother and almost calls it off (Yes, Then Zero). Later, it is revealed that Louis was giving Eliza Barnes, a therapist to Chuck, money to upset Chuck in the hope that Chuck will do something reckless and drive Blair away forever. (I Am Number Nine) Chuck publicly exposes Louis and Dr. Barnes which in turn leaves Blair devastated, as she's worried Louis is turning into Chuck. Louis also has problems trusting Blair's friends, namely Serena, Chuck, and Nate. He reveals Gossip Girl's sources after overhearing a phone conversation between Serena and Nate. Blair finds out and decides to take some space (All the Pretty Sources).
In G.G., Louis and Blair's wedding ceremony was interrupted by an explosive Gossip Girl blast, a video of Blair professing her undying love for Chuck, not Louis. Afterwards, Louis forgives Blair and continues the ceremony. However, at the reception, Louis reveals to Blair that the wedding stands as a contract and after what she did, she's going to stay his public wife for as long as he wants, as he does not love her anymore. Blair flees the wedding but is eventually tracked down by Sophie, who threatens the dowry unless she returns. Meanwhile, Eleanor informs Louis that the Waldorf's don't give into threats and his family can't control theirs. To save her family, Blair goes on her honeymoon with Louis (The Backup Dan). This episode also marks Louis' last appearance on the show. In Con-Heir, Louis and Blair's divorce is finalized.
"I can't live in this fairytale." -Blair
"I promise, this is not a story for little girls." -Double Identity (4x02)
"All my life I though I'd be married to someone I didn't love. Maybe, just maybe, that nightmare will turn into my dream." -The Princesses and the Frog (4x20)
"I was just reading about how some pregnant women have mood swings. Apparently they didn't know you before the pregnancy."
"Either you find a way to trust me or you let me go." -Blair
"I could never let you go." -Memoirs of an Invisible Dan (5x04)
"You don't have that right anymore. As a future reigning prince, it is up to my child to acknowledge you." -The Fasting and the Furious (5x05)
"Who is it?" -Blair
"Someone completely undeserving of your love and affection." -All the Pretty Sources (5x08)
"After the accident, you told me you'd never leave me. Now you feel further away than ever." -The End of the Affair? (5x11)
"I am so nervous. Can you believe it? She's marrying me. I'm the luckiest man in the world!"
"My mother told me love has nothing to do with marriage. Now I know she was right." -G.G. (5x13)
- Louis's full name was thought to have been Louis Albert Jean-Michal Grimaldi (Petty in Pink) until it was announced Louis Frédéric Grimaldi (G.G.).
- Louis had Dan write his wedding vows for him, and as a return favor, asked him to be an usher.
- He attended boarding school in Switzerland, as all Grimaldi children do.
- He enjoys visiting The Louvre and The Met.
- He enjoys tennis, equestrianism, golf, and painting.
- He attended Oxford University.