Malachi is traditionally considered the last of the Jewish biblical prophets.
In Jewish tradition, the era of classical prophecy ended with Haggai, Zechariah, and Malachi, who are associated with the post-exilic period. Malachi is conventionally treated as the final prophet in the Tanakh and the last book in its Nevi'im, or Prophets, section. His messages address religious laxity, corrupt offerings, improper priestly conduct, and failures in social and marital obligations.
The Book of Malachi is usually dated to the mid-fifth century BCE, after the Temple in Jerusalem had been rebuilt. Its closing passage looks ahead to the coming “day of the Lord” and mentions Elijah, a theme later interpreted differently in Jewish and Christian traditions.
This answer is tradition-specific. Christianity often calls John the Baptist the last prophet before Jesus, while “last prophet” can also have different meanings in other religions. The question explicitly asks about Jewish tradition, where Malachi is the standard canonical answer. Scholars also debate whether “Malachi” was the prophet's personal name or a title meaning “my messenger.”