They replace the previous district councils and county council in the county.
Simon Edwards, director of the County Councils Network, said:
“The official formation of North Northamptonshire Council and West Northamptonshire Council is an important day for the county and an opportunity to look to a brighter future – delivering high-quality services for residents and spearheading the local recovery from the pandemic.
“That they are in this position today is testament to the hard work from councillors and officers of the shadow authorities during a difficult financial period and a global pandemic. We look forward to welcoming them both into membership and working with them over the coming years.”