Mya's been holding a big secret for months ... we've learned she said "I Do" in a super-secret wedding down in Seychelles. Sources close to the singer tell TMZ ... Mya walked down the aisle back in December in a very intimate ceremony on the island nation off the African coast. We obtained these pics of her on the beach in her gown ... looking absolutely stunning. If the wedding seems like a shock to you, it is to us too. It's unclear who Mya's spouse is -- and she hasn't publicly dated anyone in years.