Siyavosh Beg,[a] also known by his nisba of Bāshīāchūghī (died c. 1650/51 or 1655), was a Safavid military commander, official, and gholam of Georgian origin.
Siyavosh Beg rose through the ranks to become a military officer (yuzbashi) early on in his career.
In 1632, he was appointed as the new governor (hakem) of Derbent and as commander of the élite gholam corps (qollar-aghasi), succeeding Khosrow Mirza (later Rostam Khan of Kartli) to this post.
When in 1645 the re-appointed grand vizier Khalifeh Sultan urged for repressive laws against Isfahan's large Armenian community, the latter turned to Siyavosh Beg, himself a former Christian.
Siyavosh Beg's nisba is derived from "Bash-Achuk", a Persian appellation of the Kingdom of Imereti, in western Georgia, where he hailed from.