That's not quite right. While Gabriel Fahrenheit did make significant contributions to thermometry, he did not invent the mercury thermometer.

Here's a breakdown:

* Mercury thermometers were invented earlier, around 1630 by Italian inventor Santorio Santorio. He was the first to use a thermometer with a scale, though his devices were quite crude.

* Fahrenheit's key contribution was improving the accuracy and precision of thermometers. He developed a reliable method for producing accurate and consistent mercury thermometers. He also introduced the Fahrenheit temperature scale, which is still used in some parts of the world.

So, while Fahrenheit was a crucial figure in the development of thermometers, the invention itself is attributed to Santorio Santorio.