The six-figure partnership, which kicks off today and will last one year, will see Lidl sponsor the site and both brands partner to co-create shareable content.
The campaign has launched with a branded homepage takeover and Lidl UK branding across Mumsnet Food’s content pages, forums and newsletters.
'Bespoke' videos from Mumsnett vloggers, who will be challenged to buy their family food shop for a week from Lidl, will also be created as part of the deal.
Lidl's marketing and advertising director Arnd Pickhardt said: "We are the supermarket that is on mums’ side, helping them to save huge sums with their weekly shop whilst still bringing home quality food for their families. We hope that this new partnership will give even more families the tools they need to become smarter shoppers.
Justine Roberts, Mumsnet CEO, added: "It’s been fascinating over the last few years to see how positive Mumsnet users have become about Lidl... We’re looking forward to creating useful, shareable content that will shake up the weekly trolley-dash."
Mumsnet has a long-standing relationship with brands in the food and drink space, including Asda, which has traditionally positioned itself as the grocer for 'mums'. The retailer has a panel of 5,000 women in its 'Mumdex' community.