With Erling Haaland strongly linked with a summer exit, Dortmund are preparing for life without the Norwegian striker, and they have identified Larsson as a potential replacement.
Hammers also want a forward after failing to replace Sebastien Haller in January, and they are keeping tabs on the Moscow star.
The 23-year-old has scored 12 goals and weighed in with five assists in 23 Russian Premier League games so far this season, and he is one of the reasons why his side are just four points behind leaders Zenit in the table.
Larsson has played primarily as a number 9 this term, but he is also very much capable of playing on the right wing.
He scored 10 goals in 30 games across all competitions last term, and his huge potential and quality should see him hit the ground running at West Ham should a move work out.
Hammers boss David Moyes could also do with such a versatile forward who would not cost much, and the fact that Dortmund also want him speaks volumes.
Larsson will be keen to prove himself outside of Sweden like his father Henrik did, and a move to the London Stadium this summer could excite him.
West Ham are likely to be playing in Europe next term from the look of things, and qualifying for the Champions League will surely boost their chances of landing the Moscow star and other top targets.