Valve's "Portal" and "Half-Life" franchises exist within the same in-game universe.

The answer is true because Valve's Portal and Half-Life franchises do indeed exist within the same in-game universe. Both franchises are set in a shared universe known as the "Half-Life universe," with occurrences from one game affecting the other. This is evidenced by several connections between the two franchises, such as references to Aperture Science (the fictional company in Portal) in the Half-Life games and characters like Gordon Freeman appearing in both franchises. The shared universe allows for a cohesive narrative and world-building, creating a seamless connection between the two popular franchises.