Based on the level of respect or formality, you can say "Congratulations on your wedding!" in Korean in 3 ways:

• Informal: gyeolhon-eul chukha-hae! (결혼을 축하해!)
• Formal: gyeolhon-eul chukha-haeyo! (결혼을 축하해요!), gyeolhon-eul chukha-hapnida! (결혼을 축하 합니다!)
• Very Formal: gyeolhon-eul chukha-deuripnida! (결혼을 축하 드립니다)

- congratulation: chukha (축하)
- to congratulate: chukha-hada (축하하다)
- your: neo-eui (너의), dangsin-eui (당신의) - omitted here
- wedding: gyeolhon (결혼), hwahon (화혼)

Please refer to How to pronounce Korean Alphabet for the English pronunciation in this answer.