The reduction of nanoelectronic devices to sub-10 nm sizes raises the prospect of electronics at the atomic scale, while also facilitating studies on nanoscale device physics. Single-atom transistors, where the current-switching element is formed by one atom and the information packet size is reduced to one electron, can create electronic switches scaled to their ultimate physical limits. Hitherto, single-atom transistor operation has been limited to low temperatures due to shallow quantum wells, which inhibit room-temperature nanoelectronic applications. Furthermore, the interaction between multiple single-atom elements at room temperature has yet to be demonstrated. Here, we show that quantum interactions between
P
dopants in
Si
/
Si
O
2
/
Si
single-atom transistors lead to room-temperature double quantum dot behavior. Hexagonal regions of charge stability and gate-controlled tunnel coupling between
P
atoms are observed at room temperature. Image processing is used to help reduce observer bias in data analysis. Single-electron device simulation is used to investigate evolution of the charge-stability region with varying capacitance and resistance. In combination with extracted tunnel capacitances and resistances, this allows experimental trends to be reproduced and provides information on the dopant-atom arrangement.