Blake Shelton & Miranda Lambert -- Divorcing

Blake Shelton and Miranda Lambert are getting divorced ... TMZ has learned.

The couple filed divorce docs a while ago, and a judge is expected to officially end their 4 year marriage today. We're told Blake is the one who filed.

We're also told all the financial arrangements have been worked out ... made easy by the fact that they have a prenup.

The divorce was filed in Oklahoma.

Our sources say he will get the ranch in Oklahoma and she'll get the family home in Nashville. Our sources say Miranda has been moving her show animals -- horses, a camel and a llama -- off the ranch in the last few days.

The couple says, "This is not the future we envisioned and it is with heavy hearts that we move forward separately. We are real people, with real lives, with real family, friends and colleagues. Therefore, we kindly ask for privacy and compassion concerning this very personal matter."

Blake's famously talked about falling in love with Miranda in 2005, when they performed a duet of "You're the Reason God Made Oklahoma."