ðə θˈiːm ʌv sˈɜːmiəm wʌzɐ bˈɪzɐntˌiːn ɐdmˈɪnɪstɹˌeɪɾɪv jˈuːnɪt θˈiːm, wˌɪtʃ ɛɡzˈɪstᵻd ɪn pɹˈɛzəntdˈeɪ sˈɜːbiə, kɹoʊˈeɪʃə ænd bˈɑːsniə ænd hˈɜːzɪɡˌɑːvɪnə ɪnðɪ ɪlˈɛvənθ sˈɛntʃɚɹi.
The Theme of Sirmium () was a Byzantine administrative unit (theme), which existed in present-day Serbia, Croatia and Bosnia and Herzegovina in the 11th century.