Eu-doped Ca2SiO4 ceramics have been newly found to show radio-photoluminescence (RPL). An as-prepared material shows photoluminescence (PL) only due to Eu3+ whereas an additional broad emission due to Eu2+ appears in the red region as a result of RPL after X-ray irradiation. The RPL is attributed to the intravalence conversion of the Eu ion (Eu3+ -> Eu2+), and this response can be detected as low as 10 mGy of X-ray dose.