Fortunately magnesium is a mineral that can be found in a wide number of foods, and here is a list of some of the richest food sources that you are going to come across.
Seeds such as sesame seeds, flaxseed, pumpkin and squash seeds, as well as sunflower seeds are some of the best ways to get the magnesium you need. 100 g of pumpkin and squash seeds are going to provide enough magnesium to fulfill the average adult male's daily requirement.
Probably preferable to most over seeds, nuts are also a fantastic source of magnesium. Brazil, cashew, pine, almonds, walnuts, peanuts, hazelnuts, all provide a great dose of magnesium.
Green leafy veg
Spinach and beet greens are good sources of magnesium, and very easy to implement into meals.
Wheat, bran, granola, quinoa, are all brilliant ways to get magnesium.
Halibut, haddock and lobster
More information on the magnesium volume in these foods can be found here:
Full list of magnesium rich foods