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 Manet. 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 there's. 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.
- Blair Waldorf (ex-wife)
Blair: "I can't live in this fairytale."
Louis: "I promise this is not a story for little girls."
4x20 − 'Je t'adore'
4x20 - Blair to Serena: "It's official, we should send out change of address cards, because I'm moving to cloud nine. Louis is incredible, with him by my side I can actually be a powerful woman."
4x20 - Blair to Serena: "Louis made me happy. Happy. Do you know the last time I felt joy? Chuck had brought me into his darkness for so long, I'd forgotten what that felt like."
4x20 - Louis to Blair: "I want you to choose joy in your life. More than that, I want to be the one who gives you joy."
4x21 - Louis to Blair: "I want you Blair. But the only way it will work is if you show me all of the parts of yourself. Even the ones you're ashamed off"
4x22 - Blair: "Louis and I it's different. It's lighter, we're simple, makes me happy."
4x22 - Chuck arrives at an empty Constance to find Louis is still there.
Chuck: "You're still here"
Louis: "Why wouldn't I be?"
Chuck: "Party's almost over."
Louis: "I know but Blair hasn't arrived yet"
Chuck: "How can you be sure she's even coming?"
Louis: "Because I love her. And just as important, I believe in her. I know she's scared, but she'll figure it out. And I'll be here when she does."
- 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.
- Belles de Jour
- Double Identity
- The Kids Stay in the Picture
- Petty in Pink
- The Princesses and the Frog
- Shattered Bass
- The Wrong Goodbye
- Yes, Then Zero
- Beauty and the Feast
- The Jewel of Denial
- Memoirs of an Invisible Dan
- The Fasting and the Furious
- I Am Number Nine
- All the Pretty Sources
- Riding in Town Cars With Boys
- The End of the Affair?
- The Backup Dan