Purchase Repertory Theatre’s production of Stephen Adly Guirgis’ “The Last Days of Judas Iscariot” is foul-mouthed, offensive, three hours long — and not to be missed.

It is daring, effective and masterfully acted by a cast of 16 Purchase conservatory students who, it is safe to assume, are only a few years removed from Broadway and feature films.

You can see them now for $20 a ticket.

If you’re lucky enough to find yourself in the Purchase College Performing Arts Center black-box space for one of the final three performances (today at 2 and 8, tomorrow at 2), you’re in for a wild ride.

The play opens with an Iscariot family pieta — Judas cradled by his mother — in an image that sets up the three hours to come: “No parent should have to bury a child,” she moans.

Next, we are in a courtroom in Purgatory, where a lawyer pleads the case for a catatonic Judas: If God is loving and just, she says, he must be merciful, too.

How could a loving, forgiving God send Judas to Hell?

A parade of witnesses, ancient and contemporary, files through the court: Mother Teresa (the wondrous Monica K. Ross); Sigmund Freud (Jason Ralph, in one of his three strong performances of the night); and Pontius Pilate (a vivid and visceral Brett Diggs).

They are examined and cross-examined by defense attorney Fabiana Cunningham (a steady and effective Olivia Osol) and by the obsequious prosecutor Yusef El Fayoumy (the hilarious James Ortiz, part used-car salesman, part rake, and always entertaining).

Other standouts in the excellent cast are Dru Smith, double cast as the Confederate Judge Littlefield and Caiaphas the Elder. As the latter, he gives one of the evening’s most earnest and heart-rending speeches, leaving the stage a broken man.

Tabitha Holbert plays Satan as a slinky, sexy steamroller of obscenity and scorching putdowns.

Natalie Woolams-Torres as Saint Monica and Julia Lawler as Mary Magdalene also impress.

The title character (Matt Lents) sits motionless through much of the action, save one extended flashback encounter with Satan. Guirgis’ Judas doesn’t wail and gnash his teeth: He’s barely breathing.

Jesus (Micah Stock) is an afterthought at the very end, softspoken and loving, the object of one of Judas’ rare lucid moments.

A. Dean Irby directs a production (by members of the school’s junior and sophomore companies) that swings effortlessly from the ridiculous to the sublime.

Ridiculous, as in El Fayoumy’s fawning over Mother Teresa.

Sublime, as in Jason Ralph’s extended monologue as Butch Honeywell, a remorseful Bostonian who comes to realize that he is dead and that he has to live with it. Butch has made a mess of his life, as he tells Judas in a wicked good Boston accent.

If the performances are strong — and they are, undoubtedly — the play has a few weaknesses.

At three hours, it could use some trimming. Guirgis, the author of “Jesus Hopped the A Train” and “Our Lady of 121st Street,” creates wonderful patchwork pieces — marvels for modern actors to deliver — but fails to connect them. The parts seem like more than the whole.

Still, the questions Guirgis raises are profound and go to the heart of faith and forgiveness. You’ll certainly leave the theater with more questions than you had going in.

How often can a $20 ticket take you on that kind of journey?

“The Last Days of Judas Iscariot”
Where: The Purchase Repertory Theatre, Purchase College Performing Arts Center, 735 Anderson Hill Road, Purchase.
When: Today at 2 and 8 p.m.; tomorrow at 2 p.m.
Tickets: $20 general admission; $15 for seniors and students.
Call: 914-251-6200.
Web: www.artscenter.org.

Purchase College photo: Tabitha Holbert as Satan and Micah Stock as Jesus square off as a catatonic Judas (Matt Lents in the center) looks on.