<p><strong>Background</strong>. Ripe papaya that does not meet standards for human consumption has the potential to be ensiled with star grass as a moisture absorber, which has the potential as an unconventional ruminant feed. <strong>Objective</strong>. To determine the quality, nutritional, and <em>in</em> <em>vitro</em> fermentative characteristics of silages made with milled ripe papaya (<em>Carica</em> <em>papaya</em> L) and star (<em>Cynodon</em> <em>nlemfluensis</em>) grass hay as moisture absorber, adding three levels of molasses during 21 and 28 days of lactic fermentation. <strong>Methodology</strong>. The silos (1.5 Kg) were made with 75% ripe papaya, 25% star grass hay, added with 2% urea and 0, 3 and 6% cane molasses; the silos were fermented for 21 and 28 d. The quality characteristics (pH, lactic acid (LA), ammonia nitrogen (N-NH₃) and dry matter (DM)), chemical characteristics (crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and ashes (As)) and <em>in</em> <em>vitro</em> fermentation (partial and accumulated production of biogas and methane (CH₄), degradation of dry matter (DDM) and degradation of neutral detergent fiber (DNDF) were evaluated). The statistical analysis was a 3x2 factorial arrangement within a completely randomized design, using level of molasses addition and fermentation time as factors. <strong>Results</strong>. pH, LA, CP and partial biogas at 24 and 48 h showed interaction between factors (p&lt;0.05). Silages with 0% molasses showed lower content of DM, As, accumulated biogas, partial CH₄ at 24 h, DDM; as well as, higher NDF, partial CH₄ at 72 h. The silages with 6% molasses presented higher DM, As, partial CH₄ at 24 h, accumulated CH₄ and DDM; in addition, lower NDF, ADF, partial CH₄ at 72 h. Silages with 21 d had lower N-NH₃, NDF, Ce, Biogas and accumulated CH₄, partial CH₄ at 24 h and 72 h than at 28 d (p&lt;0.05). The highest pH value was in silages with 28 d and 6% molasses and the highest LA in 28 d silages with 0% molasses (p&lt;0.05). <strong>Implications</strong>. Ripe papaya silage does not require cane molasses as an additive; there is no effect on the opening of the silos at 21 or 28 d of lactic fermentation. <strong>Conclusion</strong>. Silage made with ripe papaya and star grass hay as moisture absorber, with urea does not require sugar cane molasses as an additive to maintain its quality, chemical and <em>in</em> <em>vitro</em> fermentation characteristics, which allows inferring that it is an unconventional alternative in the feeding of ruminants.</p>