Who invented lettering?

Sequoyah is the only known human to invent letters who did not already know how to read.

Most writing systems were invented by humans who already knew how to read some other writing system. For example, the Cyrillic alphabet was invented by Saints Cyril and Methodius.

The oldest writing systems are generally credited to some god or goddess. For example, the goddess Carmenta is said to have invented the Latin alphabet (also called the Roman alphabet).

The Greeks credited the Egyptian god Thoth (also called Hermes) with inventing hieroglyphs and the Greek alphabet.

Ogma is said to have invented the Ogham alphabet.

The Phoenician alphabet, called by convention the Proto-Canaanite alphabet for inscriptions older than around 1050 BC, is the oldest verified alphabet and many later alphabets (e.g. Greek, Roman, English, Cyrillic) can be traced back through "evolutionary" changes to it. There is no way to determine who invented the Phoenician alphabet.

Cuneiform is one of the earliest systems of writing was developed around 3100 BC, is distinguished by its wedge-shaped marks on clay tablets. Its initial form was pictographic and was likely developed for accounting and inventory purposes among merchants, it eventually came to include a mixture of logophonetic, consonantal alphabetic and syllabic signs.