What is the rhyming scheme of a Shakespeare sonnet?

Of the 154 sonnets that Shakespeare penned, only three (Sonnets 99, 126, and 145) do not fit into what came to be known as the Shakespearean sonnet structure.
In this structure, there are exactly fourteen lines, comprising a total of three stanzas divided into four lines each. These first three lines typically present a problem or key issue of concern which is resolved in some way in the last two lines. These lines will be structurally set apart from the rest of the poem as a rhyming couplet.
The first stanza's rhyme pattern is ABAB.
The second stanza's rhyme pattern is CDCD.
The third stanza's rhyme pattern is EFEF.
And the couplet's pattern is GG.
This structure and rhyme pattern can be evidenced in the following sonnet by Shakespeare:
Shall I compare thee to a summer’s day? (A)
Thou art more lovely and more temperate: (B)
Rough winds do shake the darling buds of May, (A)
And summer’s lease hath all too short a date; (B)

Sometime too hot the eye of heaven shines, (C)
And often is his gold complexion dimm'd; (D)
And every fair from fair sometime declines, (C)
By chance or nature’s changing course untrimm'd; (D)

But thy eternal summer shall not fade, (E)
Nor lose possession of that fair thou ow’st; (F)
Nor shall death brag thou wander’st in his shade, (E)
When in eternal lines to time thou grow’st: (F)

So long as men can breathe or eyes can see, (G)
So long lives this, and this gives life to thee. (G)


(Notes for rhyme pattern have been added for clarification.)

Occasionally, you will also see this referred to as the English sonnet in form and structure.