Checkmk is a monitoring platform for hybrid IT environments and applications, developed in Python and C++. Originally released in 2009 as an extension to Nagios, it has since evolved into a standalone system that integrates infrastructure monitoring with application-level metrics. The software is developed by Checkmk GmbH (formerly tribe29), headquartered in Munich, Germany.

Checkmk was developed in 2008 by Mathias Kettner in Munich, Germany. It was developed as an extension for the Nagios monitoring system to provide alternative configuration and performance capabilities. The initial version, then styled as Check_MK, was released in April 2009 under the GNU General Public License (GPL).

In 2019, the developing company, Mathias Kettner GmbH, rebranded as tribe29 GmbH and changed the product name to Checkmk. In April 2023, the company was renamed Checkmk GmbH. In February 2025, the company announced a strategic investment from the growth equity firm PSG Equity.

In March 2026, the software nomenclature was updated. Checkmk is distributed under an Open-core model in several editions:

Checkmk provides monitoring for servers, networks, and applications. Its features include:

Checkmk employs a rule-based configuration system. Instead of configuring individual objects, parameters are defined through rules that are applied to hosts based on tags or group memberships.

Checkmk identifies monitorable components on a host via a service discovery mechanism. Data is retrieved or transmitted through the following methods:

Checkmk includes over 2,000 officially maintained integrations for hardware (servers, storage, networks), software (databases, web servers), and cloud platforms (AWS, Azure, GCP). Users can develop custom integrations using Python.