Lake St. Martin First Nation () is a Canadian First Nations government and Treaty 2 signatory.
The First Nation was based primarily at Lake St. Martin about northwest of Winnipeg until May 2011. When a massive flood hit Manitoba, the Government of Manitoba decided to divert water to Lake St. Martin in order to protect cottages and agricultural properties on other bodies of water. As a result all the housing at Lake St. Martin First Nation was destroyed. As of 2019, approximately 1,000 flood evacuees are still displaced.