Judaism
Around the 1st century CE, there were several small Jewish sects: the Pharisees, Sadducees, Zealots, Essenes, and Christians. After the destruction of the Second Temple in 70 CE, these sects vanished. Christianity survived, but by breaking with Judaism and becoming a separate religion; the Pharisees survived but in the form of Rabbinic Judaism (today, known simply as "Judaism"). The Sadducees rejected the divine inspiration of the Prophets and the Writings, relying only on the Torah as divinely inspired. Consequently, a number of other core tenets of the Pharisees' belief system (which became the basis for modern Judaism), were also dismissed by the Sadducees. (The Samaritans practiced a similar religion, which is traditionally considered separate from Judaism.)
Antisemitism in Christianity
Mainstream Talmudic Rabbinical Judaism today directly descends from the Pharisees whom Jesus often criticized. During Jesus' life and at the time of his execution, the Pharisees were only one of several Jewish groups such as the Sadducees, Zealots, and Essenes who mostly died out not long after the period; indeed, Jewish scholars such as Harvey Falk and Hyam Maccoby have suggested that Jesus was himself a Pharisee. Arguments by Jesus and his disciples against the Pharisees and what he saw as their hypocrisy were most likely examples of disputes among Jews and internal to Judaism that were common at the time, see for example Hillel and Shammai.