Eric XII Magnusson (1339-1359) was rival King of Sweden and to his father Magnus II from 1356 to his death in 1359. Married to Beatrix of Bavaria, daughter of Louis IV of Bavaria.

In 1343 Eric and his brother Haakon were elected heirs of Sweden respectively Norway. That Haakon got the Norwegian throne in 1355 (causing the union between Norway and Sweden to split) while Eric didn't get any position in the Swedish council might have affected his choice to lead a rebellion against his father in 1355. In 1357 the rebellion had forced Magnus to share Sweden with his son Eric who got to rule most of Southern Sweden and Finland. Sweden was reunited again in 1359 when father and son became reconciled, and co-ruled Sweden until the Eric's death a few months later. While dying Eric accused his mother Blanche of Namur for poisoning him. Quite soon after the death his wife Beatrix died too. It's generally believed that they were killed by the plague.