Background: An accurate estimate of expected survival time assists people near the end of life to make informed decisions about their medical care. Objectives: Use advanced machine learning methods to develop an interpretable survival model for older people admitted to residential age care. Setting: A large Australasian provider of residential age care services. Participants: All residents aged 65 years and older, admitted for long-term residential care between July 2017 and August 2023. Sample size: 11,944 residents from 40 individual care facilities. Predictors: Age category, gender, predictors related to falls, health status, co-morbidities, cognitive function, mood state, nutritional status, mobility, smoking history, sleep, skin integrity, and continence. Outcome: Probability of survival at all time points post-admission. The final model is calibrated to estimate the probability of survival at 6 months post-admission. Statistical Analysis: Cox Proportional Hazards (CoxPH), Elastic Net (EN), Ridge Regression (RR), Lasso, Gradient Boosting (GB), XGBoost (XGB) and Random Forest (RF) were tested in 20 experiments using different train/test splits at a 90/10 ratio. Model accuracy was evaluated with the Concordance Index (C-index), Harrell's C-index, dynamic AUROC, Integrated Bier Score (IBS) and calibrated ROC analysis. XGBoost was selected as the optimal model and calibrated for time-specific predictions at 1,3,6 and 12 months post admission using Platt scaling. SHapley Additive exPlanations (SHAP) values from the 6-month model were plotted to demonstrate the global and local effect of specific predictors on survival probabilities. Results: For predicting survival across all time periods the GB, XGB and RF ensemble models had the best C-Index values of 0.714, 0.712 and 0.712 respectively. We selected the XGB model for further development and calibration and to provide interpretable outputs. The calibrated XGB model had a dynamic AUROC, when predicting survival at 6-months, of 0.746 (95\% CI 0.744-0.749). For individuals with a 0.2 survival probability (80\% risk of death within 6-months) the model had a negative predictive value of 0.74. Increased age, male gender, reduced mobility, poor general health status, elevated pressure ulcer risk, and lack of appetite were identified as the strongest predictors of imminent mortality. Conclusions: This study demonstrates the effective application of machine learning in developing a survival model for people admitted to residential aged care. The model has adequate predictive accuracy and confirms clinical intuition about specific mortality risk factors at both the cohort and the individual level. Advancements in explainable AI, as demonstrated in this study, not only improve clinical usability of machine learning models by increasing transparency about how predictions are generated but may also reveal novel clinical insights.