What is the surname of Anna Karenina's lover?

The surname of Anna Karenina's lover is Vronsky.

Count Alexei Kirillovich Vronsky is a cavalry officer in Leo Tolstoy's novel Anna Karenina. He meets Anna at a railway station and becomes captivated by her, despite knowing that she is married to Alexei Alexandrovich Karenin, a senior government official.

Vronsky's courtship also affects Princess Kitty Shcherbatskaya, who expects him to propose to her. At a ball, however, he chooses to dance with Anna, making his feelings clear and leaving Kitty heartbroken. Anna and Vronsky eventually begin an affair and travel to Italy together, but their relationship becomes strained after they return to Russian society.

A common mix-up is confusing Vronsky with Karenin, Anna's husband, or Oblonsky, Anna's brother. Levin is another major character, but his storyline concerns Kitty and rural life rather than Anna's affair. Vronsky's failed horse race and Anna's growing jealousy are important developments in the novel's tragic final act.