Jonas Mačiulis (born February 10, 1985 in Kaunas, Lithuanian SSR, USSR) is a Lithuanian professional basketball player, currently playing as a small forward for the most successful Lithuanian team Žalgiris and the Lithuania national basketball team. He is 2.00m (6 ft 6 ¾ in) in height. He shares his name with the famous Lithuanian poet Maironis.
He made his debut in the LKAL with Žalgiris-Arvydas Sabonis school (2nd Team of Žalgiris) during the 2002-03 season. For the 2004-05 season signed for by the LKL team Nevėžis and was back to the first Žalgiris team for the 2005-06 season. He has an aggressive playing style and hard nosed defense; also a good rebounder, but needs to improve his passing and dribbling skills, because his future is at 2 position.