The 2019 Acura Sports Car Challenge of Mid-Ohio was a sports car race sanctioned by the International Motor Sports Association (IMSA). The race was held at Mid-Ohio Sports Car Course in Lexington, Ohio, on May 5, 2019. It was the fourth round of the 2019 WeatherTech SportsCar Championship and the first round of the 2019 WeatherTech Sprint Cup.
 International Motor Sports Association's (IMSA) president Scott Atherton confirmed the race was part of the schedule for the 2019 IMSA SportsCar Championship (IMSA SCC) in August 2018. It was the second consecutive year it was part of the WeatherTech SportsCar Championship. The 2019 Sports Car Challenge of Mid-Ohio was the fourth of twelve sports car races of 2019 by IMSA, and it was the first of seven rounds held as part of the WeatherTech Sprint Cup. The race was held at the thirteen-turn 2.258 mi (3.634 km) Mid-Ohio Sports Car Course in Lexington, Ohio on May 5, 2019.
 The event marked the inaugural event of a new support championship for the GT Daytona (GTD) class called the WeatherTech Sprint Cup. It is a championship of all the non-endurance events in the GTD calendar, using the same scoring system as the overall full-time championship, unlike its sister support championship, the Michelin Endurance Cup.
 Two and a half weeks prior to the event, Ford announced they would end their factory program with Chip Ganassi Racing in the GTLM class in both the World Endurance Championship and the WeatherTech championship at the end of 2019.
 On April 24, 2019, IMSA released a technical bulletin regarding the Balance of Performance for the race. There were no changes made to either the DPi or GT Le Mans classes. In GTD, the Lamborghini Huracán GT3, which had been victorious in the previous two rounds at Daytona and Sebring, received a 30 kilogram weight increase and a 1-liter reduction in fuel capacity. In contrast, the Audi R8 LMS and Mercedes-AMG GT3 cars were given weight reductions of 25 and 20 kilograms, respectively. The McLaren 720S GT3 received its baseline weight of 1320 kilograms and RPM of 8,000 for its first IMSA event. 
 Before the race, Pipo Derani and Felipe Nasr led the DPi Drivers' Championship with 92 points, 2 points ahead of Hélio Castroneves and Ricky Taylor in second position followed by Filipe Albuquerque and João Barbosa in third with 89 points. In LMP2, Cameron Cassels and Kyle Masson led the Drivers' Championship with 67 points; the duo held a seven-point gap over Matt McMurry and Gabriel Aubry. Earl Bamber and Laurens Vanthoor led the GTLM Drivers' Championship with 91 points, ahead of Patrick Pilet and Nick Tandy with 87 points, and Antonio García and Jan Magnussen in third with 87 points. With 70 points, Mirko Bortolotti, Rik Breukers, and Rolf Ineichen led the GTD Drivers' Championship, 16 points clear of Frankie Montecalvo, Townsend Bell, and Aaron Telitz. Cadillac, Porsche, and Lamborghini were leading their respective Manufacturers' Championships, while Whelen Engineering Racing, Performance Tech Motorsports, Porsche GT Team, and GRT Grasser Racing Team each led their own Teams' Championships.
 A total of 36 cars took part in the event split across four classes. There were 11 cars in the Daytona Prototype international (DPi) class, two in the Le Mans Prototype 2 (LMP2) class, eight entries in GT Le Mans (GTLM), and 15 entries in the GTD class.
 There were some considerable additions and changes among the field. Lone Star Racing returned to IMSA competition in the GTD class, having previously participated at Laguna Seca in 2017. Starworks Motorsport driver Parker Chase, who had previously only been on contract for the endurance events, would sign an agreement to run the full season with Starworks in 2019, alongside the existing full-season driver Ryan Dalziel. The biggest addition to the entry list, however, was Compass Racing, who would field a new McLaren 720S GT3 with factory backing in the full Sprint Cup-only campaign for the season. Their drivers were McLaren factory driver Paul Holton and Matt Plumb. On April 19, 2019, McLaren Automotive signed a multi-year agreement with IMSA in which they officially became an automotive partner of the International Motor Sports Association.
 After initially confirming full-season programs, GTD teams Precision Performance Motorsports and P1 Motorsports would not return for Mid-Ohio, with the latter pulling the plug on using their Mercedes-AMG GT3 cars in championships.
 Due to scheduling conflicts for full-season drivers Gabriel Aubry, Patrick Lindsey and Harry Tincknell, who were at Circuit de Spa-Francorchamps for the FIA World Endurance Championship, drivers Eric Lux, Marco Seefried and Ryan Hunter-Reay respectively would replace these drivers for the Mid-Ohio event.
 There were three practice sessions preceding the start of the race on Sunday, two on Friday and one on Saturday. The session on Friday morning lasted 75 minutes while the second session on Friday afternoon lasted one hour. The third session on Saturday morning lasted one hour.
 The first practice session took place at 10:05 am ET on Friday and ended with Juan Pablo Montoya topping the charts for Acura Team Penske, with a lap time of 1:41.568. Colin Braun put the No. 54 CORE Autosport second fastest in the DPi class followed by the No. 7 Acura of Ricky Taylor. Earl Bamber set the fastest time in GTLM with a time of 1:42.230, 2.208 seconds faster than Tom Blomqvist's No. 25 BMW. Trent Hindman was fastest in GTD. Neither of the LMP2 entries set a lap time. 14 of the 36 entries did not get a time in due to heavy rain.
 The second practice session took place at 3:15 PM ET on Friday and ended with Oliver Jarvis topping the charts for Mazda Team Joest, with a lap time of 1:28.158. The No. 55 Mazda of Ryan Hunter-Reay was second fastest followed by Simon Trummer in the No. 84 Cadillac. Eric Lux set the fastest time in LMP2. The GTLM class was topped by the No. 911 Porsche GT Team Porsche 911 RSR of Nick Tandy with a time of 1:32.142. Jesse Krohn in the No. 24 BMW was second fastest followed by Laurens Vanthoor in the No. 912 Porsche. The GTD class was topped by the No. 14 AIM Vasser Sullivan Lexus RC F GT3 of Jack Hawksworth with a time of 1:30.190. Zacharie Robichon was second fastest in the No. 9 Pfaff Motorsports Porsche followed by Marco Seefried in the No. 73 Park Place Motorsports Porsche. The Konica Minolta Cadillac, Whelen Engineering Racing, and Starworks Motorsport entries did not set a lap time. The session was red flagged two times. 6 minutes into the session, Ricky Taylor spun the No. 7 Acura ARX-05 at turn 12 and hit the tire barrier. Taylor got the car back to the pit lane and the session was stopped for eight minutes. The final stoppage came when Will Hardeman spun the No. 19 Audi at turn 12 and was beached in the gravel trap.
 The third and final practice session took place at 8:00 am ET and ended with Hélio Castroneves topping the charts for Acura Team Penske, with a lap time of 1:12.737. Dane Cameron was second fastest in the sister No. 6 Acura followed by João Barbosa in the No. 5 Cadillac. Kyle Masson set the fastest time in LMP2. The GTLM class was topped by the No. 67 Ford Chip Ganassi Racing Ford GT of Ryan Briscoe with a time of 1:20.100. Laurens Vanthoor was second fastest in the No. 912 Porsche GT Team entry followed by Patrick Pilet in the sister No. 911 Porsche. The GTD class was topped by the No. 86 Meyer Shank Racing Acura NSX GT3 Evo of Trent Hindman with a time of 1:21.818. Richard Heistand was second fastest in the No. 14 Lexus followed by Lawson Aschenbach in the No. 74 Lone Star Racing Mercedes-AMG. The session was red flagged two times. 4 minutes into the session, Townsend Bell's No. 12 Lexus went wide at turn 2 and got stuck in the grass. The final stoppage came when Bell's co-driver, Frankie Montecalvo went wide at the Carousel and got stuck in the grass. Montecalvo got the car back to the pit lane and the session was restarted with 6 minutes remaining.
 Saturday's late morning qualification session was broken into three groups that lasted 15 minutes each. Cars in GTD were sent out first before those grouped in GTLM and DPi/LMP2 had two separate identically timed sessions. All cars were required to be driven by one participant and the starting order was determined by the competitor's fastest lap. IMSA then arranged the grid so that the DPi, LMP2, and GTLM cars started in front of the GTD field.
 The first was for cars in the GTD class. Richard Heistand qualified on pole for the class driving the No. 14 car for AIM Vasser Sullivan. The session saw one incident when Marco Seefried, driving the No. 73 Park Place Motorsports Porsche, spun at turn two and got stuck in the grass. Seefried had his best two laps from the session deleted for causing a red flag, effectively leaving him with no time set. Zacharie Robichon was second fastest, but lost his fastest lap for not serving a drive-through penalty in the pitlane during the session's only red flag. As a result, Robichon would start from fifth position, while Ben Keating in the No. 33 Mercedes-AMG was promoted to second followed by Frankie Montecalvo's No. 12 Lexus in third position, and Will Hardeman's No. 19 Audi in fourth.
 The second session was for cars in the GTLM class. Sébastien Bourdais qualified on pole for the class driving the No. 66 car for Ford Chip Ganassi Racing, besting Laurens Vanthoor in the No. 912 Porsche GT Team entry by 0.275 seconds. Following in third was Jesse Krohn's No. 24 BMW with the No. 4 Corvette of Tommy Milner in fourth. Ryan Briscoe completed the top five in the No. 67 Ford GT followed by Connor De Phillippi's No. 25 BMW in sixth. The No. 3 Corvette Racing and No. 911 Porsche GT Team entries rounded out the GTLM qualifiers.
 The final session of qualifying was for cars in the LMP2 and DPi classes. Oliver Jarvis qualified on pole driving the No. 77 car for Mazda Team Joest, beating Hélio Castroneves in the No. 7 Acura by 0.022 seconds. Jarvis ran out of fuel on his final lap and coasted to the pitlane. Dane Cameron qualified the No. 6 Acura Team Penske entry in third position followed by Pipo Derani's No. 31 Whelen Engineering Racing Cadillac. João Barbosa in the No. 5 Mustang Sampling Racing Cadillac started from fifth place. Following in sixth was Ryan Hunter-Reay's No. 55 Mazda followed by Renger van der Zande in the No. 10 Konica Minolta Cadillac in seventh place. Kyle Masson's No. 38 Performance Tech Motorsports Oreca set the fastest time in LMP2, but the car would be dropped to the rear of the LMP2 field because the team changed their starting driver. As a result, Eric Lux was promoted to first and would start the race from pole position.
 Pole positions in each class are indicated in bold and by ‡.
 The final results of DPi kept Derani and Nasr atop the Drivers' Championship with 120 points while Albuquerque and Barbose dropped from third to fifth. Cameron and Montoya's victory allowed them to advance from fifth to fourth. The final results of LMP2 kept Cassels and Masson atop the Drivers' Championship, but their advantage was reduced to four points by race winner McMurry. With a total of 126 points, Bamber and Vanthoor's victory allowed them to extend their advantage to seven points while García and Magnussen took over second position in the GTLM Drivers' Championship. Farnbacher and Hindman took the lead of the GTD Drivers' Championship with 84 points while the absent Bortolotti, Breukers, and Ineichen dropped to sixth. Heinstand and Hawksworth advanced from seventh to third while Long jumped from sixth to fourth. Cadillac, Porsche, and Lamborghini continued to top their respective Manufacturers' Championships while, Whelen Engineering Racing, Performance Tech Motorsports, and Porsche GT Team kept their respective advantages in their Teams' Championships. Meyer Shank Racing took the lead of the GTD Teams' Championship with eight rounds left in the season.
 Class winners are denoted in bold and ‡.
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