The pair were named on Wednesday along with Rene Rast and Robin Frijns when the German manufacturer firmed up the line-ups in the two M Hybrid V8 LMDhs that will compete under the BMW M Team WRT banner during its maiden season in Hypercar.
Marciello and Wittmann will be teamed in the #15 entry with Dries Vanthoor, who was listed against the car on the publication of this season’s WEC entry list at the end of November.
Rast and Frijns will drive #20 together with Sheldon van der Linde, who was also confirmed as part of the WEC programme on the release of the entry.
Marciello moves into a role in BMW’s WEC squad as expected after joining the marque from Mercedes at the conclusion of last season.
The Italian, a kingpin of Mercedes’s GT3 roster from 2018, had been set to drive Lamborghini’s new SC63 LMDh until BMW made an approach over the summer.
BMW stalwart Wittmann moves over to a full prototype programme after making three IMSA SportsCar Championship starts last year aboard a Rahal-run M Hybrid V8 alongside his assaults on the DTM and the GT World Challenge Europe Endurance Cup with the BMW M4 GT3.
Rast and Frijns are both longtime regulars with WRT from their time as Audi factory drivers prior to moving to BMW in 2022 and 2023 respectively.
Both have raced WRT's LMP2 machinery in the WEC since it arrived in the series in 2021 and have long been regarded as certainties for its Hypercar assault.
BMW M Motorsport boss Andreas Roos said: “We have combined driving excellence with experience in the two BMW M Hybrid V8s – on the one hand experience with our LMDh car, on the other hand, experience of the race series [WEC] and the Le Mans 24 Hours in particular.
“Like Sheldon van der Linde, Marco Wittmann has already driven the BMW M Hybrid V8 in the IMSA series: all the other drivers – including our newcomer Raffaele Marciello – have already tested the car and will continue to do so intensively in the coming months.”
Marciello explained that going for “race wins and titles in the WEC, with so many big manufacturers, is exactly the challenge I was hoping for” after his move to BMW.
“Having been opponents on the racetrack for years, it is fantastic to now drive alongside Dries Vanthoor,” he continued.
“And to have a BMW M Motorsport legend like Marco Wittmann on your side is fantastic: I hope to learn from the two of them.”
Wittmann described being part of the WEC squad as “both a pleasure and an honour”.
"Having already driven the BMW M Hybrid V8 in a few races in the IMSA series, I am extremely excited about the Hypercar class in the WEC,” he said.
“There is a lot of genuine hype around this class in 2024, with so many manufacturers and top-class drivers — it is fantastic to be a part of it.”
WRT has yet to announce team-mates for Valentino Rossi and Augusto Farfus in its pair of factory-supported M4s in the new LMGT3 class.