Ivan Ivanovitch Sakharine is a model ship collector who owned an identical model ship to one that Tintin purchased at the Old Street Market in Brussels. He served as one of the two main antagonists in The Adventures of Tintin (the other being Allan Thompson).
In the books, Ivan Ivanovitch Sakharine is a collector of model ships, of which one among them is one of The Unicorn. After noticing another model of the Unicorn at a market, he and another man named Barnaby attempt to purchase it only to find that it has already been sold to Tintin. Tintin rejects all of the offers made by the two to buy the model from him. After Tintin's Unicorn is stolen he suspects Sakharine of the theft. Upon visiting Sakharine he discovers he has another Unicorn model. Sakharine is subsequently attacked by Barnaby who steals a hidden parchment from inside the second Unicorn model.Later on after the Bird Brothers are arrested, they claim that the parchments they owned, had likewise been stolen. Tintin suspects Sakharine of stealing the two parchments, but he soon discovers that it was in fact a third party and recovers them.
At the end of Red Rackham's Treasure, Sakharine can be seen attending the exhibition held at Marlinspike Hall, showing off the various items recovered from the actual ship itself. Sakharine was to appear in the last Tintin story, Tintin and Alph-Art with some other characters from various prior stories, but due to Hergé's death, the story was left unfinished. He appears in the Yves Rodier version of the book. Tintin spots him at Akass' show.
In the film adaptation The Adventures of Tintin: The Secret of the Unicorn, Sakharine is re-imagined as a replacement for the Bird Brothers as the main antagonist of the film. No longer the innocent model ship collector from said comic, he is a ruthless villain who will stop at nothing to obtain the treasure of the Unicorn from the bottom of the ocean, which he believes is property of his ancestor, Red Rackham, who was murdered by Sir Francis Haddock, the ancestor of Captain Haddock. Armed with a deadly sword concealed in his cane, a peregrine falcon for use, and thugs Tom and Allan by his side, Sakharine is willing to use any means necessary to find the treasure and lead Tintin and Haddock to their ultimate demise.
- Sakharine's last name is a play on the word "Saccharine," which is a sugar additive for tea and coffee. Therefore, it is ironic that Captain Haddock calls Sakharine a "sour-faced man with a sugary name" and that Bianca Castafiore mispronounces his name as "Sugar-Additive." Although not stated in the books, Ivan Ivanovitch is a Serbian name.