Cillium can refer to:
the Roman North African city Cillium, or Colonia Cillilana, modern Kasserine in Tunisia and the Latin Catholic titular see Cillium Cilium, an organelle Cilium (computing), a container network interface (CNI) based on eBPF, a project of Cloud Native Computing Foundation
See also Caput Cilla, Ancient city and titular see in present Algeria