The pastel drawing, given to Second Officer Charles Lightoller, an unsung naval hero and the last man rescued, was made by a mystery passenger or crewman on the doomed ship.
Lightoller, then 28, ordered 'women and children first' into the lifeboats. He kept the drawing until he died in 1952 - and it is now to be auctioned among his mementoes, reports The Sun.
Auctioneer Andrew Aldridge said: "It shows the moment of sinking, with the stern hanging in the air and lifeboats rowing away.
"It's slightly inaccurate as it shows four funnels intact when we now know two had broken off, but it is a very good sketch."
The sale is on Apr 18.