Windows Live OneCare（或onecare、LIVE ONECARE。中文名称未定，Onecare意一份关心）是微软Windows Live旗下的杀毒软件，是微软进入安全防护领域的第一个杀毒软件。已经停止出售，并且所有产品和帐单支持均已终止，但微软仍然提供免费的同类软件Microsoft Security Essentials供经过正版验证的用户使用。

该软件功能包括ProtectionPlus（杀毒，防间谍，防火墙，自动更新）、PerformancePlus（硬盘整理，垃圾清理，自动备份）、Backup and Restore（备份+恢复），同时OneCare也与Windows Update合作，以提供自动视窗系统更新，OneCare也备有即时帮助（24小时／7天）。

Windows Live OneCare (previously Windows OneCare Live, codenamed A1) was a computer security and performance enhancement service developed by Microsoft for Windows. A core technology of OneCare was the multi-platform RAV (Reliable Anti-virus), which Microsoft purchased from GeCAD Software Srl in 2003, but subsequently discontinued. The software was available as an annual paid subscription, which could be used on up to three computers.