Which of 2 Valve Games are set in the same universe?

Half-Life and Portal are set in the same universe because they share multiple elements and references throughout their respective narratives. Both games take place in the Aperture Science Enrichment Center, which is mentioned in Half-Life 2, establishing a connection between the two worlds. Additionally, Portal includes the iconic "Black Mesa" references, which is the research facility and main setting of Half-Life. This suggests a cohesive universe and reinforces the notion that both games exist in the same overarching storyline, known as the Half-Life/Portal universe.