Co-written and first recorded by Ed Bruce (C&W #15 1975).
Other hit version by Waylon Jennings & Willie Nelson (US #42/C&W #1/CAN #1 1978).
From the wiki: “‘Mamas Don’t Let Your Babies Grow Up to Be Cowboys’ was first recorded in 1975 by Ed Bruce, written by him and his wife, Patsy Bruce. Bruce’s rendition of the song peaked at #15 on the Hot Country Singles charts in 1975.
“Waylon Jennings and Willie Nelson covered the song on their 1978 duet album Waylon & Willie. This cover recording peaked at #1 on the Hot Country Singles chart in March 1978, spending four weeks topping the chart while also crossing-over to the Billboard Hot 100. In 1979, the song won the Grammy Award for Best Country Performance by a Duo or Group with Vocal. Members of the Western Writers of America have also chosen ‘Mamas Don’t Let Your Babies Grow Up to Be Cowboys’ as one of the Top 100 Western songs of all time.”