Morris' hit "Girl" and the Zac Brown Band's "Someone I Used to Know" will go head-to-head for the Video of the Year prize, alongside the likes of Carrie Underwood ("Cry Pretty"), Dan + Shay ("Speechless"), Kacey Musgraves ("Rainbow"), and Keith Urban and Julia Michaels ("Coming Home").
The top category features 14 contenders, but only the five with the most fan votes will make the final shortlist, which will be unveiled on the morning of the 5 June ceremony.
"Girl" will also compete for Female Video of the Year, again pitting Morris against Underwood for "Love Wins", and Musgraves for "Space Cowboy", while Lambert's "Keeper of the Flame", Brandi Carlile's "The Joke", "Miss Me More" by Kelsea Ballerini, and "Closer to You" from Carly Pearce round out the competition.
Lambert scores a mention in the Male Video of the Year group thanks to her Jason Aldean collaboration "Drowns the Whiskey", which will face off with promos including Luke Bryan's "Sunrise, Sunburn, Sunset", "Life Changes" by Thomas Rhett, and Eric Church's "Desperate Man".
"Drowns the Whiskey" is also featured in the running for Collaborative Video of the Year.
Meanwhile, the Zac Brown Band's other two nominations are for Group Video of the Year and CMT Performance of the Year, after hitting the stage with pop star Shawn Mendes for a rendition of the band's 2011 song, "Keep Me in Mind", which they played for an episode of music show CMT Crossroads.
Underwood's two new nominations give her the opportunity to extend her lead as the artist with the most CMT Music Awards in history - she currently has 18.
Singer Carly Pearce, whose tune "Closer to You" earned her a nod for Female Video of the Year, helped to announce the main categories on U.S. breakfast show "Today" on Tuesday, May 07.
Double nominees Little Big Town will return for the second consecutive year to host the prizegiving in Nashville, Tennessee next month.
The nominations for the 2019 CMT Music Awards are:
Video of the Year:
Female Video of the Year:
Male Video of the Year:
Duo Video of the Year:
Group Video of the Year:
Breakthrough Video of the Year:
Collaborative Video of the Year:
CMT Performance of the Year: