Is it true, Jesus was a Jew?

Yes, Jesus was a 1st-century Galilean Jew who lived, taught, and was crucified within the traditions of Judaism.

Life and Practice
Birth and Heritage:
Jesus was born to a Jewish mother named Mary in the region of Galilee and traced his lineage to Abraham and King David.
Religious Observance:
He followed the Torah, attended synagogues, observed Jewish holidays like Passover, and wore traditional ritual fringes on his garments.
Role as Rabbi:
He functioned as a Jewish religious teacher, or rabbi, and his moral teachings expanded upon foundational Hebrew scripture.

Historical and Religious Context
First Followers:
His immediate family, disciples, and earliest followers were all Jewish.
Christianity's Roots:
According to the Encylopedia Britannica on Jesus (as outlined in mainstream historical consensus), the movement that eventually became Christianity originated entirely within a Jewish framework before developing into a distinct, separate faith.

If you'd like, I can explore:
How early Christian writers interpreted Jesus' Jewish identity
The historical relationship between first-century Judaism and the early church