This paper explores the search for large-gap quantum spin Hall (QSH) insulators in tin films, which are crucial for both fundamental and practical applications. Using first-principles calculations, the authors find that two-dimensional tin films exhibit QSH states with bulk gaps of 0.3 eV, suitable for room-temperature applications. These states can be tuned by chemical functionalization and external strain. The QSH effect is attributed to band inversion at the Γ point, similar to HgTe quantum wells. Surface doping with magnetic elements can also realize the quantum anomalous Hall effect. The study highlights the potential of tin films for dissipationless conduction and high-speed electronics, with the ability to pattern helical edge states for use in electronic circuits. The work is supported by the Defense Advanced Research Projects Agency and the DARPA Program on "Topological Insulators – Solid State Chemistry, New Materials and Properties."This paper explores the search for large-gap quantum spin Hall (QSH) insulators in tin films, which are crucial for both fundamental and practical applications. Using first-principles calculations, the authors find that two-dimensional tin films exhibit QSH states with bulk gaps of 0.3 eV, suitable for room-temperature applications. These states can be tuned by chemical functionalization and external strain. The QSH effect is attributed to band inversion at the Γ point, similar to HgTe quantum wells. Surface doping with magnetic elements can also realize the quantum anomalous Hall effect. The study highlights the potential of tin films for dissipationless conduction and high-speed electronics, with the ability to pattern helical edge states for use in electronic circuits. The work is supported by the Defense Advanced Research Projects Agency and the DARPA Program on "Topological Insulators – Solid State Chemistry, New Materials and Properties."