The crash involving three vehicles happened at 6.45am on Sunday, February 16 on the southbound carriageway near junction seven, Harlow.
Emergency services attended, and the woman was taken to hospital with serious injuries.
Two other people were also taken to hospital with injuries that are not life-threatening or life-changing.
A man in his 50s, from Coventry, was arrested on suspicion of drink driving and remains in custody for questioning.
The road was closed while emergency services dealt with the incident.
Essex Police are now appealing for any witnesses or anyone with dashcam footage to come forward.
A spokesman for Essex Police said: “Officers investigating a serious collision on the M11 are appealing for any witnesses or anyone with dashcam footage to come forward.
“We were called to a collision at around 6.45am on Sunday, February 16, involving three vehicles on the M11 southbound prior to Junction 7 near Harlow.”
Anyone with any information or footage is asked to contact police, citing incident 175 of February 16.
