Fuel ethanol production has dramatically increased in the world. Ethanol fermentation for alcohol beverages is a traditional and mature technology. However, the fermentation technology for fuel ethanol should be reconsidered because it must be large scale and low cost. High-temperature fermentation is the most promising approach for efficient fuel ethanol production from the viewpoints of cost-reduction and robustness. In addition, high temperature is helpful to establish simultaneous saccharification and fermentation process because sugar hydrolyzing enzyme activities can be enhanced. For the high-temperature fermentation, thermotolerant ethanol-producing yeasts are indispensable. In this chapter, yeast strains suitable for high-temperature bioethanol fermentation are reviewed. Among these, Kluyveromyces marxianus achieved sufficient ethanol production in a pilot-scale high-temperature fermentation from starch contained in waste cassava pulp. Strain improvement has also been conducted to establish further cost-effective high-temperature ethanol fermentation. In addition, the studies of thermotolerant mechanisms will be helpful to get the strains suitable for high-temperature fermentation through genetic engineering.