The police were alerted about the incident in Papartynai village, District of Šakiai, on Wednesday morning.
The single mother allegedly threw her 7-month-old baby into a well intentionally, but immediately had a change of heart and alerted a neighbour who rushed to the well and pulled out the boy.
The baby was taken to hospital and is feeling well, DELFI reports.
The neighbour, identified by DELFI as Algimantas Brazaitis, said his neighbour ran into his house screaming at about 9 AM and said she had killed her child.
He said the baby was not breathing when he pulled it out. Brazaitis resuscitated the boy while the mother herself called the ambulance.
Police officers later said the mother could be mentally disturbed.
Local community leader Dalius Jasevičius has told BNS that the woman is a single unemployed woman who currently lives at her father's house.
He says the family has not been flagged as potentially troublesome.