Dallas Cowboys superstar Dak Prescott and his fiancée, Sarah Jane Ramos, are not getting married — TMZ Sports has learned the two have broken up one month before their wedding.

We’re told the relationship had been rocky behind the scenes for months … but things came to a head with a blowup argument at their joint bachelor and bachelorette parties in the Bahamas — and Sarah Jane called it off.

She actually shared several snaps from her bachelorette party with her closest friends earlier this week … captioning the post, “I truly believe you can get through anything in life as long as you have really great friends. I love these girls so much.”

The reality is, we’re told the relationship is beyond repair … so the focus will be on coparenting their two kids — ages 2 and nearly 10 months — moving forward.