In the Gospel of Matthew, it says that Judas Iscariot threw the 30 silver coins down in the Temple and went out and hanged himself.  Not knowing what to do with this blood money, the chief priests used it to buy the potter's field; a field to be used to bury foreigners.¹  The potter's field (the Field of Blood) is the field Judas Iscariot hanged himself in.²

In the Gospel of Matthew, it says that the chief priests purchased the field.  And in the book of Acts, it says that Judas Iscariot purchased the field. 

At first reading, it would seem that the two accounts contradict themselves; they don't however.  What had happened is that the chief priests used the money that Judas Iscariot had thrown into the Temple to purchase the potter's field in Judas' name; as it was purchased in his name, in all actuality it was purchased by him.

Bible References:

¹ (Matthew 27:5-8)

² (Acts 1:19)