Ethanol is produced by yeasts and used for different applications. The ever-increasing demandrnfor energy necessitates the production of ethanol as biofuel to supplement fossil fuels as a sourcernof energy and protect the environment from environmental pollution. This requires for selection of effective ethanol producing local yeasts to produce ethanol from easily available agriculturalrnwastes. To this end, indigenous yeasts were isolated from yeast habitats such as traditionalrnfermented beverages, soil, flower, and compost samples collected from different part of Ethiopia.rnThe isolates were screened for their glucose fermentation and ethanol production.. The selectedrnyeast isolates with better ethanol production from glucose were identified using 26S rRNArnsequence analysis using NL1 and NL4 primers. They were further evaluated for their ability tornferment different carbon sources, sedimentation rate, tolerance to sugar and ethanolrnconcentration. Production of ethanol by selected yeasts was optimized based on variables such asrninoculum size, temperature, pH, and incubation time using response surface methodology basedrnon central composite design. Enzymatic, acid, and alkali hydrolysis, and coculture werernemployed to produce ethanol from grass pea and wild oat straws and starch. In order to producernethanol from whey, experimental runs such as molasses and external nutrient supplementation,rneffect of whey pH, sterilized and non-sterilized whey were evaluated. Five isolates werernidentified as Saccharomyces cerevisae and the remaining three were grouped into Kluveromycesrnmarxianus, Pichia fermentans and Candida humilis. The pattern of sugar utilization showed thatrnonly K. marxianus ETP87 and P. fermentans ETP22 were able to grow on xylose; and K.rnmarxianus ETP87 was the only yeast that fermented lactose and, therefore, was selected tornproduce ethanol from whey. All the 8 yeasts other than C. humilis were able to flocculate arnfeature that makes the biomass separation easy for industrial applications. Regarding tolerance tornethanol, S. cerevisae ETP53, K. marxianus ETP87, P. fermentans ETP22 and C. humilis ETP122rnwere tolerant to 10% extraneous ethanol but the percentage of ethanol tolerance considerablyrndecreased at 15% and 20% ethanol shock treatment. S. cerevisae ETP53 produced ethanolrnoptimally at pH 5.0, 60 hours, and 34oC; whereas the optimal growth and fermentation by Krnmarxianus ETP87 was at pH 4.8, temperature 36oC, and incubation time of 65 hours. Highestrnreducing sugar was released from 1% (v/v) H2SO4 and 1% (w/v) NaOH treated straws; wherernsulfuric acid yielded higher amount of sugars than NaOH, and more ethanol was obtained fromrnalkali hydrolysates. Significant amount of furfural was liberated from acid hydrolyzed straw thatrnwas reduced by treatment with activated carbon and overliming. The data also showed thatrnsignificant amount of sugars was released from fungi (Pleurotus ostreatus M2191, Pleurotusrnsajor-caju M2145, Trichoderma reesei JCM22676, and Aspergillus niger JCM22344) grown onrnstraws solid state media than enzymatic and chemically treated straws. However, the ethanolrnxivrnproduction from fungal-treated straws was small. It was also established that higher ethanolrnproduction was obtained from acid-hydrolyzed sorghum flour than the one produced from crudernamylase enzyme treated substrate and ethanol derived from coculturing, indicating thatrnsimultaneous saccharification and fermentation is a promising method to produce ethanol fromrnstarch. The data also showed that K. marxianus ETP87 was capable of producing ethanol fromrnnon-sterilized and non-deproteinized substrates. The effect of nutrient supplementation to wheyrnwas variable depending on the kind of nutrient added. Generally, it could be concluded that S.rncerevisiae ETP53, K. marxianus ETP87, and P. fermentans ETP22 are promising yeasts tornproduce ethanol from different substrates at acidic pH, near 35oC and late fermentation time.