The suspect attacked the man while he was asleep, reported The Independent.
Police said the woman bought the weapon two weeks before inviting her husband to stay in her apartment in Ijebu-Ode, a city in the south-west of Nigeria.
She waited for him to go to sleep, police told Nigeria’s The Nation newspaper, before hacking at him with the new machete.
The man was taken to the Ijebu-Ode General Hospital, where he remains in a coma, though doctors suggested he was responding well to treatment. Graphic images published in local media reports showed a man lying on a hospital bed, with deep wounds to his chest, shoulders and legs.
On Tuesday, images emerged showing a woman believed to be Ms Etu standing against a wall, holding what appeared to be the machete involved in the attack.
Ijebu-Ode’s acting police spokesman, Abimbola Oyeyemi, said the weapon used in the attack had been recovered.