This letter demonstrates for the first time junctionless (JL) gate-all-around (GAA) poly-Si thin-film transistors (TFTs) with ultrathin channels (2 nm). The subthreshold swing is 61 mV/decade and the ON/OFF current ratio is close to 10 8 because of the excellent gate controllability and ultrathin channel. The JL-GAA TFTs have a low drain-induced barrier lowering value of 6 mV/V, indicating greater suppression of the shortchannel effect than in JL-planar TFTs. The cumulative distribution of electrical parameters in JL-GAA is small. Therefore, the proposed JL-GAA TFTs of excellent device characteristics along with simple fabrication are highly promising for future system-on-panel and system-on-chip applications.Index Terms-Gate-all-around (GAA), junctionless (JL), thin-film transistor, ultrathin channel.