The Manchu alphabet
The Qing dynasty (ruling China from 1644-1912) was founded by a clan of Manchuria, who spoke the Manchu language, written in the Manchu alphabet. Prior to the Qing dynasty defeating the Ming dynasty, Manchu leader Nurhaci
decided to convert the Mongolian alphabet to make it suitable for the Manchu people. He decried the fact that while illiterate Han Chinese and Mongolians could understand their respective languages when read aloud, that was not the case for the Manchus, whose documents were recorded by Mongolian scribes. Overriding the objections of two advisors named Erdeni and G'ag'ai, he is credited with adapting the Mongolian script to Manchu. (Wikipedia)
The Manchu people are culturally and linguistically distinct from the Han Chinese and the Sino-Tibetan Chinese languages, but for centuries, even millenia, the Manchu people had been ruled by various successive dynasties of China, so that I think it's appropriate to call them a Chinese people, and not a foreign occupier. In fact, they had been the ruling dynasty of northern China previously, from 1115 to 1234 (the Jin dynasty, ruled by Jurchen people, who later renamed themselves the Manchu.)
The Manchu language was an official language of the Qing dynasty, although it was never the only language used, and its use in China decreased over time, until by the 19th century it was in severe decline. But the script was still used on occasional official documents until the dynasty was overthrown in 1912. The script is derived from the Mongolian alphabet, and can be traced back to the Phonecian alphabet, via Aramaic.
The Manchu alphabet was also occasionally used to write Chinese, perhaps most notably for the famous Thousand Character Classic poem.
Here it can be seen beside a parallel inscription in Chinese on a stele of the Kangxi Emperor (reigned 1661-1722):
And here it is, again besides Chinese, on a plaque at the Forbidden City:

