There are community-developed "Unofficial Service Pack 3" projects . These typically bundle all official updates up to 2023 (and sometimes unofficial patches to extend support further).

Before attempting to install the rollup or later updates, your system must have: already installed. Servicing Stack Update (SSU) from April 2015 or later. How to Get the Closest Alternative to SP3

Microsoft’s official updates for Windows 7 stopped receiving mainstream feature packs; security and quality updates were distributed via Windows Update or standalone KB packages. After SP1, Microsoft issued security-only and rollup updates (and the Extended Security Updates program for eligible customers). There is no documented MS release named "SP3."

In 2016, Microsoft released a "Convenience Rollup" (KB3125574). This single package contains nearly all security and non-security updates released between SP1 and April 2016, leading many to unofficially call it "Service Pack 2" or even "Service Pack 3".