In the live action films Transformers and Transformers: Revenge of the Fallen, Optimus Prime is the leader of the Autobots. Prime now transforms into a conventional Peterbilt 379 cab, rather than the cab over design of his original Generation 1 body. Also straying from the G1 design, Prime's vehicle mode is now decorated with red flames painted onto a blue body (à la Rodimus Prime, his Generation 1 successor), often incorrectly rumored to be inspired by NASCAR driver Jeff Gordon's current paint scheme at the time. The reason for the change was due to Director Michael Bay's decree that no "mass displacement" occurs when they transform, thus requiring Optimus's vehicle form to have more mass to achieve the desired size in his robot form. Michael Bay stated Optimus stands 28 feet, but in an interview, ILM's Scott Farrar stated "The movie's Optimus Prime is 32 feet tall and made of 10,108 parts - and every single one had to be modeled and painted when they came within camera range. This puts him on the same height as the movie's Starscream and 2 to 4 feet shorter than Megatron as well in the film."

Although redesigned to some extent like the other characters in the film, some classic design elements remain in his robot mode, including a predominantly red torso, primarily blue legs, the presence of windows in his chest, smoke stacks on his shoulders, and a head design influenced by the original, featuring the iconic faceplate and ear finials. This faceplate is able to retract to reveal a mouth. His weapons include an energy rifle that unveils from his back, two retractable energon blades that extend from both forearms (a homage to Prime's energy axe in the Generation 1 animated series), Ion cannons on both of his arms, as well as two retractable energon hooks on both of his forearms. In the later IDW comics he displays the ability to produce a holographic driver mentioned in the early versions of the script. The appearance of this driver seems to be based on Peter Cullen himself.

It was publicly announced at San Diego ComicCon 06 that original Optimus Prime voice actor Peter Cullen would reprise his role for the film. Cullen has commented that Prime is basically the same, and retains the same basic personality

Optimus Prime arrives on Earth at the same time as Ironhide, Jazz and Ratchet, landing in a field. He scans the new alternate mode of a semi-truck and quickly joins up with Bumblebee and his human companions. The Autobots then go with Sam Witwicky to retrieve his ancestor's glasses, on which a map to the All Spark is engraved. While waiting for Sam and Mikaela to find the glasses, Optimus and his comrades inadvertently destroy the backyard of Sam's parents. They recover the glasses, but a secret government organization, Sector 7, arrests Sam and Mikaela, and capture Bumblebee. Before it is discovered, Sector 7 also has a frozen Megatron hidden under Hoover Dam, Ironhide questions Prime on why they should protect the humans, seeing them as primitive and violent. Prime replies that the Autobots themselves were not so different from them once, quoting "Freedom is the right of all sentient beings." Before the final battle with Megatron, he says, "By the end of this day, one shall stand, one shall fall." This is a tribute to the 1986 animated film, in which Optimus Prime delivers the line, "One shall stand, one shall fall." before his final battle with Megatron.

While evacuating the All Spark from Hoover Dam, Optimus Prime attempts to thwart the Decepticon Bonecrusher's pursuit. After a short battle, Prime beheads Bonecrusher with his retractable blade. Although Prime fights Megatron in a final battle, Sam kills Megatron ramming the All Spark into his chest. Prime, who had planned to destroy the All Spark by placing it into his own chest, is immensely grateful to Sam for saving him. Afterwards, Optimus then takes the remaining fragment of the All Spark. Despite all that has happened, Prime deeply regrets Megatron's death, evidenced by his parting words: "You left me no choice, brother." In the comic adaptation of the film Optimus and Megatron refer to each as "brother" several times, but in the film, only once. What "brother" means to a Cybertronian is never explained in the film.

Like the other Autobots featured in the film, he chooses to remain on Earth after the battle with the Decepticons. The film ends with Optimus sending out a deep-space signal, inviting other Autobots to join them on Earth.

Optimus Prime returns in Transformers: Revenge of the Fallen, taking down in Shanghai, China, the massive Decepticon Demolishor. Before his death, Demolishor warns Optimus that "The Fallen shall rise again". Later, U.S. defense advisor Galloway chastises Optimus for the damages done during the fight and deems that the Decepticons only remain on Earth to hunt down the Autobots. Though Optimus warns him that there's a chance he might be wrong while telling him the Autobots would leave if requested, he attempts to ask Sam for help. He later fights (and overpowers) Megatron, Starscream and Grindor on his own to protect Sam from the three Decepticons. Though he manages to kill Grindor, and rip Starscream's arm off, Optimus is destroyed by Megatron, who stabs him in the chest from behind, killing him as he searches for Sam. However, learning that the Matrix could revive Optimus (who is the only one capable of defeating the Fallen, since being the last Prime), Sam has his body transported to Egypt for the final battle. He is revived once Sam puts the Matrix of leadership into his circuits. However, the Fallen steals the Matrix soon afterward and uses it to power the Sun Harvester. Jetfire sacrifices his life to give his parts to Optimus. With the help of Ratchet and Jolt, Optimus uses parts from Jetfire as a flying armor and successfully kills the Fallen, forcing Megatron and the Decepticons to retreat. At the end of the film he again transmits a message to space in hopes to find more Autobots.