Water is a critical natural resource, a global public good, and an essential service. Water security is central for countries to achieve long-term development objectives in the current context of climate change, including protecting infrastructure assets, safeguarding agricultural production, producing sustainable energy, and protecting vulnerable populations. However, water resources are under severe stress and water services delivery is deficient due to underinvestment in the sector. Current levels of global investment in water are inadequate to meet the water sustainable development goals (SDGs) and address climate impacts. Large, coordinated flows of public, concessional, and private capital are needed to compensate for decades of underinvestment in the water sector, and to meet present and future challenges. Governments have a leading role to play in establishing the enabling conditions and necessary reforms to facilitate a greater flow of public and private finance for required water sector investments. International financial institutions and multilateral development banks need to support these efforts, together with other stakeholders, at the country level. The private sector, in addition to being a key user of water resources and a beneficiary of water services, has an important role to play in providing financing, innovative approaches, and expertise, as well as absorbing risk, with aligned incentives for achieving targets and efficiency levels.