P&P: Getting started - Social Classes and Titles

Class difference was of course a fact of life for Austen, and an acute observation of the fine distinctions between one social level and another was a necessary part of her business as a writer of realistic fiction (Copeland, 1997: 115).
Although in her own life Austen did have some dealings with royalty, however mediated, when she was graciously invited to dedicate Emma to the Prince Regent, she never presents royalty in her fiction, nor any of the great aristocrats who still owned great tracts of the country, and were prominent in its government.(Copeland, 1997: 116).

Royalty (Your Majesty/ Your Highness)

• King
• Queen 
• Prince
• Princess

Nobility (Lord/Lady)

• Duke
• Duchess
• Marquis
• Marquise
• Earl
• Countess
• Viscount
• Viscountess
• Baron
• Baroness

Commoners (Sir/Lady, Mr/Mrs)

• Knight
• Landed gentry
• "Pseudo" gentry 

To distinguish a nobel lady from a non-noble lady, the first name of the noble women was used.
Eg: Lady Catherine de Bourgh is a noblewoman whereas Lady Lucas is the wife of a commoner.

Other Gentlemen (Mister or rank title such as Captain, Colonel)

• Affluent businessmen
• Navy and army officers (Follow this link to know more about hierarchy within this group)
• Clergymen

References:

Copeland, E.; McManter, J. (1997) The Cambridge Companion to Jane Austen. Cambridge: CUP.

Warren, R. (2008). Rank and Class of the Regency Period. [Online] Retrieved from:
https://www.janeausten.org/rank-and-class.asp (Accessed, April 5th, 2019)

(2011) Titles and Precedence. An Explanation of English Titles. [Online] Retrieved from:https://www.janeausten.co.uk/titles-and-precedence/ (Accessed, April 5th, 2019)