The Church takes no official stance on this, but some members believe that the legendary Sasquatch or Bigfoot is Cain. The main source that usually is used to back this theory is the reminiscence of Abraham Smoot of a story from one of the Church's first apostles, David W. Patten. Patten claimed that in 1835 he encountered Cain walking along the side of the road. He wrote: "He walked along beside me for about two miles. His head was about even with my shoulders as I sat in my saddle. He wore no clothing, but was covered with hair. His skin was very dark."
We can see how someone could get Bigfoot from that description. The Smoot/Patten story was also quoted in Spencer W. Kimball's book, The Miracle of Forgiveness. In the 1980's, there was a Bigfoot sighting in South Weber, Utah and many members used this story to explain how and why these sightings occurred.
On the sad character Cain, an interesting story comes to us from Lycurgus A. Wilson's book on the life of David W. Patten. From the book I quote an extract from a letter by Abraham O. Smoot giving his recollection of David Patten's account of meeting "a very remarkable person who had represented himself as being Cain.
'As I was riding along the road on my mule I suddenly noticed a very strange personage walking beside me… His head was about even with my shoulders as I sat in my saddle. He wore no clothing, but was covered with hair. His skin was very dark. I asked him where he dwelt and he replied that he had no home, that he was a wanderer in the earth and traveled to and fro. He said he was a very miserable creature, that he had earnestly sought death during his sojourn upon the earth, but that he could not die, and his mission was to destroy the souls of men. About the time he expressed himself thus, I rebuked him in the name of the Lord Jesus Christ and by virtue of the holy priesthood, and commanded him to go hence, and he immediately departed out of my sight…"
(Miracle of Forgiveness, Spencer W. Kimball, (1969) p 127
"Bigfoot and Mormons?" in MormonNews - Link is here.
"Bigfoot, the Three Nephites and the Lost Tribes of Israel" on Mormon Matters - Link is here.
"Cain is Bigfoot" at Mormon Monsters - Link is here.