Although the Bible mentions a number of wealthy individuals, the richest person by far was King Solomon. His reign is described in the first half of the book of I Kings in the Old Testament. Interestingly enough, he did not ask for wealth. The story says that the Lord appeared to Solomon in a dream at night and asked what he should give him. Instead of requesting riches, honor, long life, or the defeat of his enemies in battle, Solomon requested an understanding heart, to be able to wisely judge his people. The request pleased God so much that he gave Solomon what he asked for, which was a wise and understanding — and also all the other things that he didn't ask for, as a bonus.
It takes the Bible several chapters to describe all of Solomon's wealth. He accumulated it in various ways. For instance, he sent out vessels for trading to Tyre, in what is now Lebanon, and the coast of Africa. These ships came back with gold, silver, ivory, and other valuable items. He heavily taxed his own subjects and also received tribute from the rulers of nearby lands. Additionally, visiting dignitaries brought him gifts. Notable among his visitors was the Queen of Sheba, who supposedly arrived with a great train of camels bearing gold, precious gems, spices, and other riches.
The Bible says that Solomon built two immense palaces, and within these palaces, all the cups and other vessels were made of gold, and none were made of silver. There was so much gold in Solomon's kingdom, in fact, that silver was considered as worthless as stones on the ground. Solomon also had an immense throne built of ivory overlaid with gold.
To give a rough idea of the Biblical estimation of a portion of Solomon's wealth, chapter 10 of I Kings says that Solomon received 666 talents of gold every year. According to Oxford Biblical Studies, a talent was about 75.5 pounds in our measurement. This means that Solomon's income included over 50,000 pounds of gold every year.