Which scientist's lectures did Pasteur attend at the Sorbonne?

The scientist whose lectures Pasteur attended at the Sorbonne was Jean-Baptiste Dumas.

Pasteur heard Dumas’s chemistry lectures while preparing in Paris in the early 1840s. Dumas was one of France’s leading chemists, known for work on organic compounds, atomic weights, and molecular analysis. His clear, energetic teaching strongly influenced the young Pasteur’s decision to pursue chemistry.

Pasteur later entered the École Normale Supérieure in 1843 and continued building the experimental skills that shaped his career. Dumas remained an important scientific influence and later supported Pasteur professionally. Pasteur’s early training under influential chemists helped connect his studies of crystals and molecular asymmetry with his later research on fermentation and microbes.

A common mix-up is Claude Bernard, another major nineteenth-century French scientist associated with Pasteur. Bernard worked with Pasteur on blood and urine experiments in 1862, but he was not the Sorbonne lecturer identified in this question.