The accused identified as P Rama Rao flung acid on the woman, who is the mother of three children, at Vankailapadu village in Prakasam district last night, they said.
Rao and the woman, who lost her husband some time back, were allegedly having an "illicit" affair for the past several years. However, she recently refused to continue the relationship, which angered him.
The woman received burn injuries on her face, stomach and legs, a police officer said, adding that she has lost her eyesight in the incident.
A case has been registered and efforts are being made to trace the accused.
