Jay Leno is taking steps to manage his wife's affairs ... in the form of a conservatorship.
The comedian filed legal docs Friday to become conservator of his wife Mavis Leno's estate ... according to court records.
A source with direct knowledge tells TMZ ... Jay's wife suffers from Alzheimer's disease.
The diagnosis, our source says, is the basis of the conservatorship ... meaning Jay's wife may not have the wherewithal to take care of herself.
We've seen Jay out in public with Mavis as recently as November, when they were photographed together at a comedy event in Los Angeles.
It's unclear when Jay's wife was diagnosed with Alzheimer's -- a progressive disease that starts with memory loss and is the most common type of dementia.
Jay and Mavis have been together for decades ... tying the knot way back in 1980 after meeting in the 1970s at the famous Comedy Store in West Hollywood.
The couple does not have any kids, a decision Mavis takes full credit for. At 77, Mavis is 4 years older than Jay.