Telemarketing (sometimes known as inside sales, or telesales in the UK and Ireland) is a method of direct marketing in which a salesperson solicits prospective customers to buy products, subscriptions or services, either over the phone or through a subsequent face to face or web conferencing appointment scheduled during the call. Telemarketing can also include recorded sales pitches programmed to be played over the phone via automatic dialing.

Telemarketing is defined as contacting, qualifying, and canvassing prospective customers using telecommunications devices such as telephone, fax, and internet. It does not include direct mail marketing.

The two major categories of telemarketing are business-to-business and business-to-consumer.

Telemarketing may be done from a company office, from a call center, or from home. It may involve a live operator voice broadcasting which is most frequently associated with political messages.

An effective telemarketing campaign often involves two or more calls. The first call (or series of calls) determines the customer's needs. The final call (or series of calls) motivates the customer to make a purchase. Prospective customers are identified by various means, including past purchase history, previous requests for information, credit limit, competition entry forms, and application forms. Names may also be purchased from another company's consumer database or obtained from a telephone directory or another public list. The qualification process is intended to determine which customers are most likely to purchase the product or service.

In business-to-business lead generation scenarios, telemarketing often targets perceived decision-makers who might be good prospects for a business product or service. The telemarketing approach is often combined with outreach via email or social media, typically referred to as a cadence. Calls are usually made by sales development representatives with the goal of this outreach being a subsequent meeting—often with an account executive at the vendor organization.

Charitable organizations, alumni associations, and political parties often use telemarketing to solicit donations. Marketing research companies use telemarketing techniques to survey the prospective or past customers of a client's business to assess market acceptance of or satisfaction with a particular product, service, brand, or company. Public opinion polls are conducted similarly.

Telemarketing techniques are also applied to other forms of electronic marketing using e-mail or fax messages, in which case they are frequently considered spam by receivers.