Final answer:
Finland is the country separated from Sweden by the Gulf of Bothnia, both of which are Nordic countries with low population densities.
Step-by-step explanation:
The country that is separated from Sweden by the Gulf of Bothnia is Finland. As two of the Nordic countries, Sweden and Finland have vast areas with low population densities, especially when compared to other European nations.
Sweden, the fourth largest country in Europe, has less than 10 million people, while Finland, along with Norway and Denmark, all had populations of less than six million people as of the 2017 census.