Background: Sexually active older adults are often more susceptible to HIV and other sexually transmitted infections (STIs) due to various health conditions (especially a weakened immune system) and low use of condoms. We aimed to assess the global, regional, and national burdens and trends of HIV and other STIs in older adults from 1990 to 2019. Methods: We retrieved data from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 on the incidence and disability-adjusted life-years (DALYs) of HIV and other STIs (syphilis, chlamydia, gonorrhoea, trichomoniasis, and genital herpes) for older adults aged 60–89 years in 204 countries and territories from 1990 to 2019. Estimated annual percentage changes in the age-standardised incidence and DALY rates of HIV and other STIs, by age, sex, and Socio-demographic Index (SDI), were calculated to quantify the temporal trends. Spearman correlation analysis was used to examine the relationship between age-standardised rates and SDI. Findings: In 2019, among older adults globally, there were an estimated 77327 (95% uncertainty interval 59443 to 97 648) new cases of HIV (age-standardised incidence rate 7·6 [5·9 to 9·6] per 100000 population) and 26414267 (19777666 to 34860678) new cases of other STIs (2607·1 [1952·1 to 3440·8] per 100 000). The age-standardised incidence rate decreased by an average of 2·02% per year (95% CI –2·38 to –1·66) for HIV and remained stable for other STIs (–0·02% [–0·06 to 0·01]) from 1990 to 2019. The number of DALYs globally in 2019 was 1905 099 (95% UI 1670056 to 2242807) for HIV and 132 033 (95% UI 83512 to 225630) for the other STIs. The age-standardised DALY rate remained stable from 1990 to 2019, with an average change of 0·97% (95% CI –0·54 to 2·50) per year globally for HIV but decreased by an annual average of 1·55% (95% CI –1·66 to –1·43) for other STIs. Despite the global decrease in the age-standardised incidence rate of HIV in older people from 1990 to 2019, many regions showed increases, with the largest increases seen in eastern Europe (average annual change 17·84% [14·16 to 21·63], central Asia (14·26% [11·35 to 17·25]), and high-income Asia Pacific (7·52% [6·54 to 8·51]). Regionally, the age-standardised incidence and DALY rates of HIV and other STIs decreased with increases in the SDI. Interpretation: Although the incidence and DALY rates of HIV and STIs either declined or remained stable from 1990 to 2019, there were regional and demographic disparities. Health-care providers should be aware of the effects of ageing societies and other societal factors on the risk of HIV and other STIs in older adults, and develop ageappropriate interventions. The disparities in the allocation of health-care resources for older adults among regions of different SDIs should be addressed.