MS Stena Baltica is a RoPax ferry, owned by Stena Line and operates on the Baltic Sea between Nynäshamn, Sweden and Ventspils, Latvia. The ship previously operated on the Irish Sea, between Birkenhead and Belfast, as Stena Mersey.

Stena Line is a Swedish shipping line company and one of the largest ferry operators in the world. It services Denmark, France, Germany, the United Kingdom, Ireland, Latvia, the Netherlands, Norway, Poland, Finland and Sweden. Stena Line is a major unit of Stena AB, itself a part of the Stena Sphere. It is a sister company to one of the world's leading tanker company Stena Bulk.