2018 Argentine Republic motorcycle Grand Prix

The 2018 Argentine Republic motorcycle Grand Prix was the second round of the 2018 MotoGP season. It was held at the Autódromo Termas de Río Hondo in Santiago del Estero on 8 April 2018. In the MotoGP class, Jack Miller scored his first MotoGP pole position.

Having been declared a wet race at the time of the sighting lap, all but one rider selected rain tires. Pole-sitter Jack Miller being the only rider to initially go out on slick tires. Prior to the warm-up lap, every rider on rain tires elected to return to the pits to change to slick tires. Returning to the pits after the sighting lap usually results in the rider starting the race from pit-lane, however, the race officials deemed it a safety concern to have all but one rider start from pit-lane. The start of the race was delayed due to the unusual situation. Eventually, the grid was reset positioning the entire field in their original qualifying positions, but filling the grid from the rear. The result was Jack Miller (who didn't return to the pits for a tire change) in the first position on the grid and the other riders in formation several rows back.

After the warm-up lap, Marc Márquez stalled his motorcycle while lining up on the grid. Attempting to restart his bike, Márquez pushed the motorcycle away from his grid position. He was successful in restarting the stalled motorcycle, but race officials ran out and instructed him to return to pit-lane. Márquez ignored the race officials' instructions, proceeded to ride his motorcycle back in the opposite direction toward his original starting position and rejoined the rest of the riders who were all waiting for the race start. After jumping to an early lead, Marc Márquez was issued a ride-through penalty for riding his motorcycle in the opposite direction on the track. Rejoining near the back of the field, Márquez began advancing position passing slower riders. In his attempt to regain positions, Márquez was issued a second penalty when he collided into Aleix Espargaró being required to drop a position for irresponsible riding. Márquez earned his third penalty of the race for crashing into yet another rider. This time he collided into Valentino Rossi in the closing stages of the race, resulting in Rossi being pushed onto the wet grass where he fell. Rossi was able to remount and finish the race, but was unable to secure any points after being taken out by Márquez. Márquez continued to finish the race in 5th position, which would have earned 11 championship points, but receiving a 30-second time penalty after the race for crashing into Rossi put him outside of a points earning position. In this race, Marc Márquez earned 3 separate penalties.

In the closing laps there were multiple passes for the podium positions between Zarco, Rins and Crutchlow as the riders struggled with tire wear and damp patches on the track.

Cal Crutchlow took Honda's 750th victory and became the first non-factory rider to lead the championship since Sete Gibernau in the 2004 Catalan Grand Prix, as well as the first British rider to lead the championship since Barry Sheene in 1979. Repsol Honda failed to score for the first time since the previous year's event.