The Goliath beetles (Goliathus) are among the largest beetles. In my opinion only 2 or 3 specieses are heavier or larger. There are a lot of claims that Goliathus goliatus, Goliathus orientalis or Goliathus regius are the heaviest beetles or even insects with weight up to 100 gr (3.5 oz), but it is very unlikely, according to University of Florida a large living Goliathus goliatus of approximately 10 cm total length was recently reported to weigh 42 grams (C. Campbell, pers. comm.). The same extrapolation of data would produce a figure of about 45 grams for a living 11 cm Goliathus, that mean 3 or 4 grams fewer than the largest reported Megasoma actaeon – 13.5 cm. On the photo Goliathus regius on men arm.
Source: Wikipedia, Extreme Science, University of Florida, Natural Worlds
See more: The Largest Beetle - part I, The Largest Beetle - part II