The second incarnation of Viacom Inc. ( VY-ə-kom or VEE-ə-kom; a portmanteau of Video & Audio Communications) was an American multinational mass media conglomerate with interests primarily in film and television, which was formed as a spin-off of the original Viacom on December 31, 2005. It was one of two companies which succeeded the first Viacom, alongside the second incarnation of CBS Corporation; both were owned by National Amusements, a theater company controlled by businessman Sumner Redstone. The spin-off was structured so that CBS Corporation would be the legal successor to the first Viacom, with the second Viacom being an entirely separated company.

The second Viacom operated Viacom Media Networks, through which it controlled approximately 170 networks and reached approximately 700 million subscribers in approximately 160 countries. Viacom's studio assets included Paramount Pictures, MTV Films, and Nickelodeon Animation Studio, as well as a 30% ownership stake in the Rainbow S.p.A. animation studio. CBS Corporation retained the over-the-air broadcasting, television production, pay television subscription service, and publishing assets, which were previously owned by the first Viacom. The second Viacom was the world's ninth-largest media company in terms of revenue, and headquartered at One Astor Plaza in Midtown Manhattan, New York City.

The second merger between Viacom and CBS Corporation, creating the combined ViacomCBS company, was announced on August 13, 2019; the merger was completed on December 4, 2019.