The public health context in developing countries is challenged in its ability to adequately provide and sustain essential health information systems to support healthcare delivery and management. A problem identified in relation to the efforts in addressing this challenge is a lack of emphasis on local imperatives and resource-constrained considerations in the design and implementation of information systems. This contributes to ineffectiveness of solutions and poor sustainability capacities. On this basis, this thesis explores frugal digital innovation and its potential for addressing challenges in resourceconstrained contexts. The research is motivated on the realisation that leveraging on established local systems and infrastructures can enhance resource utilisation efficiency, solutions viability, and capacity strengthening for sustainability. The public sector focus also has socio-economic development implications as scarce resources can be wasted in pursuit of non-practicable and unsustainable solutions. The research was carried out in the public health context of Sierra Leone and concerning the DHIS2 software between 2017 and 2019. The aims were first to contribute to efforts at strengthening the national health information systems infrastructure and second to advancing the scholarly knowledge in the field of information systems research. With a frugal digital innovation lens data was qualitatively collected and analysed guided by the interpretive paradigm. The findings suggest that positioning frugality at the core in digital innovations can contribute positively towards efficiency and sustainability in resource-constrained settings. As contribution to theory the thesis emphasises the mutual constitutionality of frugal innovation principles and innovation capabilities of digital technologies in a dynamic process-outcome relationship conceptualised as continuous, overlapping, and iterative. For the broader information systems field this perspective contributes to clarifying that the functional scope in digital technology-enabled innovations is extensible; innovation agency can be distributed in an ecosystem, and innovation processes and outcomes being interchangeable also means that they are not distinctly different phenomenon. Practically, a frugal digital innovation strategy is proposed to leverage existing systems, infrastructures, and resources. In this strategy, general project design principles for guiding solution architects and policy makers are proposed to; focus on addressing the prevailing user problem and contextual challenges; explore possibilities for building on established social and technological infrastructures; and consider reusing institutionalised structures. Furthermore, specific solution implementation options are proposed to include; leveraging software platform features for new solutions; scaling general IS functionalities into specific use cases, scoping domain specific systems for use in other organisational domains; and embedding new and complementary solutions into existing pa...