Throughout his life and career, Shelley was a political radical, a strong opponent of the Establishment into which he had been born. In particular, he was no respecter of kings, as his support for the republican cause in his native Britain illustrates. "Ozymandias" can be seen, then, as an expression of Shelley's contempt for monarchs and all their worldly pretensions. Ozymandias saw himself as a great pharaoh, whose name and earthly achievements would live on indefinitely. Yet he, like everyone else, eventually passed away; and the statue he erected as a monument to his own greatness now lies crumbling in the sands of the desert.

Even in Shelley's day, even in the wake of the French Revolution, many kings and queens believed that they had the God-given right to rule. They too believed like Ozymandias that their names were destined to live on for all eternity. But Shelley wishes to remind them in no uncertain terms of their mortality and how true greatness does not reside in one's titles or public monuments, but in the heart and in the soul.

Shelley wrote "Ozymandias" for several reasons. First, the poem was inspired by the arrival in England of a portion of a statue of the ancient Egyptian pharaoh Ramesses II. Shelley wanted to commemorate that event and was spurred on as well by a friendly rivalry with the poet Horace Smith. Smith also wrote a poem about the statue at the same time as Shelley, and he also called it "Ozymandias." 

As a radical who had supported the French Revolution, Shelley used the poem as a commentary on tyranny. In the poem, Ozymandias understands himself as as invincible tyrant, and imagines all who see his mighty kingdom and mighty statue tremble with fear. However, Shelley ironically shows the statue as a wrecked ruin strewn across an empty desert. Ozymandias' once powerful kingdom has disappeared. The statue's inscription--'Look on my works, ye Mighty, and despair!'--thus has a double meaning. Seeing now the ruin of Ozymandias' works, the "mighty" might despair by realizing even the most powerful tyrannies become nothing. 

What was Shelley's purpose in writing "Ozymandias?"

Ozymandias, also known as Ramesses II, was an Egyptian Pharaoh. He was a powerful ruler and is still one of the most well-known Pharaohs today. Percy Shelley, in his poem, was reflecting on Egyptian monuments. The British people were extremely interested in learning about Egypt at this time, and many historical pieces were being imported to English museums.

Shelley's purpose for writing this poem was actually to win a contest. He and his friend Horace Smith agreed to participate in a sonnet-writing contest. They both chose the subject of Egypt and wrote their poems. Both sonnets eventually got published in newspapers, so both writers were fairly successful in their competition.

Though Shelley wrote his sonnet to win a contest, he has a clear message about fame in his poem. Through the life of Ozymandias, Shelley shows the brevity of life and fame. No person, even the great and mighty Ozymandias, is immortal. All eventually die; their fame dissipates. This is the sad message behind Shelley's sonnet.

What was Shelley's purpose in writing "Ozymandias?"

In my opinion, Shelley's purpose was to encourage the reader to think about how futile it is to try to become famous.  He may also be applying that idea to his own attempts to be a famous poet.

In this poem, Shelley is using the character of Ozymandias to show us how fame is fleeting.  He looks at how this man, who was important enough to rule a huge kingdom, is now an unknown.  The only way anyone knows about him is by his fallen statue in the middle of the desert -- no one knows anything about his kingdom or his deeds.

In this way, Shelley is showing us that even the people who seem important slip into obscurity, so it is pointless to try to be "someone."

What is Shelley's purpose in writing "Ozymandias"?

The purpose of a poem is to express a theme or create a mood.  In Shelley's "Ozymandias," the theme becomes clear with the last lines:

"My name is Ozymandias, king of kings: 

Look on my works, ye Mighty an despair!"

Nothing beside remains.  Round the deay

Of that colossal wreck, boundless and bare

The lone and level sands stretch far away.

Ozymandias is probably a reference to the Egyptian pharaoh Ramses II, who built impressive statues, pyramids, and kingdoms.  His proud boast, which is written on the ruins of a statue of him, is a vain and an empty one because nothing remains of his works.  With the exception of these broken ruins, all has disappeared into the sand.  Shelley shows us man's attempt to immortalize himself through his works.  But he shows that such attempts are futile.  Time and nature ("sand" symbolizing both) will eventually overcome all our works, no matter how great and impressive the works once were.  

Correlated with Ozymandias's attempts to make a permanent mark are the sculptor's attempts as well.  

 . . .its sculptor well those passions read

Which yet survive, stamped on these lifeless things,

The hand that mocked them, and the heart that fed . . .

The sculptor also showed skill in his works, but little of that skill remains--a "shattered visage," "trunkless legs," and "a pedestal."  Just as a king's works do not remain, an artist's works are temporary.  Both the hand of the sculptor who fashioned the original sculpture and the heart of the pharaoh which inspired it are no more.  Men and their works are mortal.  

Shelley's purpose is to remind us of this cold hard fact, and perhaps instill humility in the minds of his readers.   

The  link below contains a thorough discussion of the poem, its themes and techniques.  

What is the main point of writing the poem "Ozymandias"?

The overarching theme of the poem "Ozymandias" is the transience of human life and its achievements. Ozymandias was a great Egyptian pharaoh, otherwise known as Ramasses II, who once built a huge statue of himself. But now, due to the passing of several centuries, the statue lies in ruins, reduced to a sad collection of fragments decaying in the desert. However, the pedestal still remains, and the inscription on that pedestal reads as follows:

My name is Ozymandias, king of kings:
Look on my works, ye Mighty, and despair!

The inscription is an expression of the pharaoh's monumental arrogance. He genuinely believed that his deeds upon this earth would make him immortal. Yet his great statue lies in ruins, showing that however grand, however important we think we are, we must all one day succumb to the ravages of time.