Abstract The 2012 EQUAL GROUND study, Towards a LGBT Stigma and Discrimination Index for Sri Lanka, produced systematic evidence of stigma and discrimination experienced by lesbian, gay, bisexual, transgender and intersex (LGBT) people across Sri Lanka, but stopped short of the composite instrument its title promised. This paper addresses that gap. Drawing exclusively on the published aggregate data from the 2012 study, it constructs the Sri Lanka LGBT Stigma and Discrimination Index (SLSDI): a four-domain composite instrument scored on a zero to one hundred scale, grounded in minority stress theory (Meyer, 2003), structural stigma scholarship (Link and Phelan, 2001; Hatzenbuehler, 2009), and composite indicator methodology (OECD/JRC, 2008). The four domains capture external stigma and discrimination, structural and institutional discrimination, internalised stigma, and disclosure safety. The SLSDI 2012 baseline score is 32.05 under equal domain weighting and 30.77 under theory-based weighting, placing Sri Lanka firmly in the Moderate band on both measures. A sensitivity analysis across five weighting scenarios confirms this finding across a range of 30.77 to 34.91, all Moderate. Domain-level analysis reveals that external stigma (42.96, High) and disclosure safety (41.35, High) impose the greatest measurable burden, while structural discrimination scores substantially lower (14.45, Low), a pattern explained by the avoidance behaviour captured in the internalised stigma domain; a mechanism consistent with Hatzenbuehler’s (2009) structural stigma internalisation framework. Within Domain C, the fear experiences sub-score of 43.85 (High) substantially exceeds the behavioural decisions sub-score (16.09, Low), confirming that anticipatory stigma operates well beyond its formal incidence. The sentinel indicator of suicidal ideation (26.89 percent) is excluded from the composite on clinical-ethical grounds and reported separately as a finding of independent urgency. The methodology is transparent, fully documented, and designed for longitudinal replication.