Ennis Del Mar[nb 1] is the fictional main character of the short story "Brokeback Mountain" by Annie Proulx, the 2005 Academy Award-winning film adaptation of the same name directed by Ang Lee, and the 2023 play by Ashley Robinson also adapted from the short story.

Ennis's story is depicted by his complex sexual and romantic relationship with Jack Twist in the American West, over two decades from 1963 to 1983.

In an interview about her work, and "Brokeback Mountain" in particular, Proulx stated Ennis Del Mar was a "confused Wyoming ranch kid" who finds himself in a personal sexual situation he did not foresee, nor can understand.

He has sexual and emotional relationships, of varying and fluctuating degrees, with Jack, his wife Alma, and his girlfriend Cassie.

Sex researcher Fritz Klein stated he felt Ennis to be "a bit more toward the straight side of being bisexual.

The film's producer James Schamus and LGBT-related non-fiction author Eric Marcus opined that the characters were both gay.

Hartinger personally "felt it inconceivable" that the characters could be considered bisexual and not gay because the film consistently showed their dissatisfaction with their heterosexual partners and deep emotional and physical fulfilment with one another.

For Hartinger, the actors' opinions of "straight guys who just happened to fall in love" seem to come more from Gyllenhaal and Ledger's acting method rather than an assessment of the text.

While on a 1963 shepherding job on Brokeback Mountain in Wyoming, Ennis meets and falls in love with rodeo cowboy Jack Twist.

Eventually they switch roles, with Jack taking over duties at base camp and Ennis tending the flock.

One night, after the two share a bottle of whiskey, Ennis decides to remain at the base camp overnight instead of returning to the sheep.

The weather becomes bitterly cold that night, but Ennis is reluctant to sleep in the same tent as Jack, who insists he join him.

Unwilling to leave his family and haunted by a childhood memory of the murder of a suspected homosexual couple in his hometown, Ennis fears that such an arrangement can only end in tragedy.

While she explains what happened, Ennis imagines Jack being beaten to death by a group of men wielding tire-irons.