Do you mean the clothes celebrities wear when they announce/get engaged (the photos, red‑carpet reveal and street‑style “I’m engaged” looks) or the jewelers who make engagement rings? Below I cover both — short list of the fashion designers and the jewelry houses most commonly associated with celebrity engagement moments.

Clothing designers and labels (engagement announcement outfits, photos, casual “I’m engaged” looks)

• Dior — couture and ready‑to‑wear used for formal announcement looks and red‑carpet reveals.
• Chanel — classic, photographed a lot on high‑profile couples.
• Valentino — romantic gowns often chosen for announcement or engagement‑party appearances.
• Alexander McQueen — dramatic, bridal‑adjacent pieces used for engagement or proposal‑to‑wedding transitions.
• Gucci — visible in both polished and eclectic engagement‑announcement outfits.
• Saint Laurent — sleek, modern looks for urban “I’m engaged” street or evening photos.
• Miu Miu — youthful, feminine dresses that show up in many celeb engagement looks.
• Zimmermann — popular for romantic daytime or boho engagement‑photo dresses.
• Self‑Portrait — widely used for stylish announcement/on‑the‑go dresses (affordable, photogenic).
• Reformation — frequently chosen for casual, sustainable engagement photos and proposal outfits.
• Carolina Herrera / Monique Lhuillier / Vera Wang — while primarily bridal, often worn during engagement parties or press reveals when the look is bridal‑leaning.

Jewelry houses (engagement rings and statement pieces)

• Tiffany & Co. — iconic engagement rings and engagement announcements.
• Cartier — classic, high‑profile engagement rings and pieces.
• Harry Winston — known for celebrity engagement diamonds.
• Graff — ultra‑high‑carat stones favored by some celebrities.
• Van Cleef & Arpels — luxury, recognizable styles.
• Bvlgari — bold, signature pieces sometimes used for engagement rings.
• De Beers — diamond specialist with celebrity clients.
• David Yurman / Neil Lane — well known for both celebrity rings and red‑carpet jewelry.

How these are used in practice

• Engagement ring = jewelry house (above). Celebrities often publicize the ring brand in photos and interviews.
• Announcement outfit = mix of couture (for formal reveals) and accessible/instagrammable brands (for lifestyle/casual announcement shots). Many celebrities pick romantic designers for photos and trendier contemporary labels for candid, everyday announcement images.

If you’d like, I can:

• Give examples of specific celebrity engagements and the brands they wore/used, or
• Suggest brands at different price points if you’re shopping for an engagement‑photo outfit or ring.