Beef bones are traditionally used for phở bò broth. The bones are simmered for several hours to extract gelatin, minerals, and savory flavor, creating the clear, deeply flavored stock that defines Vietnamese beef pho.
A classic broth may combine beef bones with oxtails or bones that still carry meat, then add charred onion, ginger, and spices such as star anise, cinnamon, coriander seed, fennel, clove, and black cardamom. Cooks commonly skim impurities from the surface to keep the broth clean and clear, adding fish sauce near the end for seasoning.
This does not mean every pho broth is beef-based. Phở gà uses chicken bones and meat, while modern restaurants may offer vegetarian or other regional variations. The name phở bò specifically identifies the beef version, so “beef” is the canonical answer for this question. The broth’s beef connection also reflects French colonial-era changes in meat availability, although pho’s precise origins remain debated.