Three vehicles and a cyclist were involved in the accident on Wainfleet Road at Croft Bank, near to the Top Farm Caravan Site.
A 46-year old man died and his passenger in her 40s was left with life-threatening injuries.
The incident took place just before 3.30pm on yesterday (Sunday, June 6).
Police say a blue Mini, which was travelling east towards Skegness, collided with a black Peugeot 208 which was travelling towards Wainfleet.
The man driving the Mini was sadly pronounced dead at the scene, and the woman who was his passenger in the Mini was airlifted to Hull Royal Infirmary by Lincolnshire and Nottinghamshire Air Ambulance. She remains in a critical condition.
A white Vauxhall Mokka and a cyclist were also believed to be involved. The cyclist, who was wearing shorts and a high vis vest, initially stopped at the scene and we are asking that she contact us to help with the investigation.
Police are also asking for anyone who was in the area at the time and saw anything, or who may have dashcam footage, to call them on 101 quoting incident 310 on 6th June.
The road was closed until around 11pm last night. This latest fatality brings the total number of people killed on Lincolnshire’s roads this year to 10.