Maurice Robinson, 25, is due to appear at Chelmsford Magistrates’ Court tomorrow.
He is charged with 39 counts of manslaughter, conspiracy to traffic people, conspiracy to assist unlawful immigration and money laundering.
Robinson, who is known as Mo and is from Northern Ireland, was arrested shortly after the bodies of eight women and 31 men were found in the refrigerated trailer in an industrial park in Grays on Wednesday.
Another man wanted by Essex Police as part of the investigation was arrested at Dublin port today.
Gardai said the man, who is in his early 20s and from Northern Ireland, was held over an unrelated outstanding court order and will appear in court on Saturday afternoon.
Three other people arrested over the deaths, including a 48-year-old man from Northern Ireland who was detained at Stansted Airport on Friday on suspicion of conspiracy to traffic people and manslaughter, remain in custody.
It comes after the Vietnamese ambassador to the UK met with Police as they work to identify the bodies.