leading figure; foremost person
Refers to the most prominent or influential person in a particular field, organization, or movement. Often used in formal or journalistic contexts.
He is a leading figure in Japanese robotics.
この分野の第一人者として、彼女は多くの講演を行っている。
As a foremost expert in this field, she gives many lectures.
He is the leading figure in modern medicine.
She is active as a leading figure in robotics.
He became the leading figure in that field within a few years.
先駆者 means a pioneer who was first to do something, while 第一人者 means the person currently at the top of a field.