Panionios B.C. (Greek: Πανιώνιος KAE) is the Greek professional basketball club that plays its home games in Nea Smyrni, Athens, Greece. The club is also widely known as Πανιώνιος Γυμναστικός Σύλλογος Σμύρνης, or Panionios Gymnastikos Syllogos Smyrnis, which is the Pan-Ionian Gymnastic Association of Smyrna. This is usually abbreviated to the club name of Πανιώνιος Γ.Σ.Σ. Panionios B.C. is the basketball department of the Panionios Gymnastic Club that is based in Nea Smyrni, Athens, Greece. The team’s colors are blue and red.

Panionios B.C. has been a long-time club of the Greek Basket League, which is considered one of the best domestic basketball leagues in Europe. Recently, Panionios B.C. has also competed in the Euroleague. For sponsorship reasons, the club has also recently been known as Panionios On Telecoms, and Panionios Forthnet. The owner of the club is Elias Lianos, the founder of Proton Bank.

Well-known players that have played with the club over the years have included: Fanis Christodoulou, Boban Janković, Panagiotis Giannakis, Theo Papaloukas, Žarko Paspalj, Thurl Bailey, P.J. Brown, Mitchell Wiggins, Travis Mays and Nikos Oikonomou.