Konstantin Treplev
Arkadina's son and an aspiring playwright. He's talented but fragile, and he ties his self-worth entirely to whether his mother and Nina approve of him. When both reject him, he has nothing left to stand on. His arc ends in suicide.
Nina Zarechnaya
A young woman from a neighboring estate who dreams of becoming an actress. She falls for Trigorin's glamour, follows him to Moscow, and pays a serious price. By Act Four she has lost almost everything but keeps working. She survives where Konstantin doesn't.
Irina Arkadina
A famous actress and Konstantin's mother. She's vain, possessive of Trigorin, and largely indifferent to her son's suffering. She's not a monster. She just puts herself first, consistently, and the people around her absorb the cost.
Boris Trigorin
A celebrated novelist and Arkadina's lover. He's charming and passive. He pursues Nina when she's available and returns to Arkadina when things get complicated. He doesn't intend cruelty but causes it anyway through inattention and self-interest.
Masha
The estate manager's daughter. She's in love with Konstantin and knows he'll never love her back. She marries Medvedenko out of resignation, not affection. She drinks, she's sardonic, and she represents what happens when you give up on wanting things.
Sorin
Arkadina's brother and owner of the estate. He's old, ill, and full of regrets about the life he didn't live. He wanted to be a writer and a city man. He became neither. He's fond of Konstantin and largely powerless to help him.
Medvedenko
A schoolteacher who loves Masha and eventually marries her. She doesn't love him. He's earnest and financially stressed, and the play uses him to show how little love matters when it's not returned.