Probably the next most important people in Judaism after God are Abraham, Isaac and Jacob (also known as the Patriarchs) who are considered to be the founding fathers of Judaism. What is believed to
be so special about those men is that it was with them that God established the covenant, meaning a unique relationship with him, which started with Abraham with the promise that he would be the father of a new nation, and was renewed with Isaac and Jacob. This covenant is at the heart of Jewish belief, and it's from there that the Jewish people received the term of "chosen" people. Abraham especially is recognized as being the first Jew (the first "chosen" one) because he was the person that was chosen by God to set an example amongst a polytheistic nation and went on to teach others that there was just one God.
Another very important person in the Jewish belief is Moses, who is considered to have been sent by God to free the Jewish nation who had become slaves in Egypt, and take them to the Holy Land they had been promised. It was also to him that God gave the sets of rules which the Jews should abide by, and which are still followed today with some variations depending wether they are Orthodox, Reformists or Conservative.
A woman who is a very significant character in Judaism is the queen Esther, Jewish wife of the king Ahasuerus that reined in the year 365 BC. With her uncle Mordechai, Esther foiled the plot of Hamman, the prime minister, to exterminate the Jews, and by risking her life she saved the Jewish nation from being exterminated. The famous Jewish holyday of Purim celebrates the deliverance of the Jewish people by Esther.
Besides those people there are the 15 judges whose story is related in the Bible - who were the leaders of the Jewish people for close to 350 years of Jewish history, or kings such as David and prophets such as Daniel and Jeremiah, all who contributed in Jewish history and are also important, but the patriarchs and the others mentioned above would be the main characters related to the Jewish faith.