The former "Rust" armorer -- who was convicted of manslaughter for her role in Hutchins' death -- received a sentence of 18 months behind bars Monday in front of a New Mexico judge. She'll serve her time at a women's correctional facility in the state.

Hannah was able to speak before learning her fate ... addressing the court directly and pleading for mercy -- but more specifically, for probation. Obviously, the judge didn't bite.

Gutierrez-Reed was the first person to stand trial for the death of the "Rust" cinematographer. Remember, Hutchins was killed by a live round of ammunition fired from a prop gun Alec Baldwin was holding ... "Rust" director Joel Souza was also injured in the shooting.

Over the course of the 2-week criminal trial, the prosecution painted Gutierrez-Reed as reckless and careless at her job -- so much so, they claimed, that it amounted to criminal negligence. Yet, HGR's defense team claimed she was an easy scapegoat for the tragedy.

Ultimately, the jury sided with the prosecution ... they found Gutierrez-Reed guilty of involuntary manslaughter. However, the jury found her not guilty of evidence tampering.

HGR faced a potential 18-month prison sentence and a $5,000 fine heading into Monday's sentencing -- and she received the maximum penalty.

Following the verdict, Hutchins' family spoke out in a statement, noting they were satisfied with the outcome. They added at the time ... "We look forward to the justice system continuing to make sure that everyone else who is responsible for Halyna's death is required to face the legal consequences for their actions."