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: “‘Mammas Don’t Let Your Babies Grow Up to Be Cowboys’ was first recorded in 1975 by Ed Bruce, written by him and wife Patsy Bruce. Bruce’s rendition of the song went to number 15 on the Hot Country Singles charts. Waylon Jennings and Willie Nelson covered the song on their 1978 duet album Waylon & Willie. This recording peaked at #1 in March 1978, spending four weeks atop the Country music charts while also crossing-over to the Billboard Hot 100, and won the 1979 Grammy Award for Best Country Performance by a Duo or Group with Vocal. Members of the Western Writers of America chose ‘Mamas Don’t Let Your Babies Grow Up to Be Cowboys’ as one of the Top 100 Western songs of all time.”
Waylon Jennings & Willie Nelson, “Mamas Don’t Let Your Babies Grow Up to Be Cowboys” (1977):