dei_EntityRegistrantName

TRANSAMERICA SERIES TRUST

rr_SupplementToProspectusTextBlock

TRANSAMERICA SERIES TRUST

Supplement to the Currently Effective Prospectus, Summary Prospectuses

and Statement of Additional Information

* * *

Transamerica Goldman Sachs 70/30 Allocation VP

Transamerica PineBridge Inflation Opportunities VP

* * *

Transamerica Goldman Sachs 70/30 Allocation VP

Effective as of August 28, 2020, the portfolio will lower its management and sub-advisory fee schedules as described below.

The “Annual Fund Operating Expenses” table included in the “Fees and Expenses” section of the Prospectus and Summary Prospectus is deleted entirely and replaced with the following:


Class		Service
Management fees¹		0.10%
Distribution and service (12b-1) fees		0.25%
Other expenses²		0.04%
Acquired fund fees and expenses²		0.70%
Total annual fund operating expenses		1.09%

¹

Management fees have been restated to reflect a reduction in management fees effective August 28, 2020.

²

Other expenses and acquired fund fees and expenses are based on estimates for the current fiscal year.

The “Example” table included in the Prospectus and Summary Prospectus is deleted entirely and replaced with the following:

Example: This Example is intended to help you compare the cost of investing in the portfolio with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the portfolio for the time periods indicated and then redeem all shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the portfolio’s operating expenses remain the same. The Example does not reflect charges that are, or may be, imposed under your variable life insurance policy or variable annuity contract. If such charges were reflected, costs would be higher. Although your actual costs may be higher or lower, based on these assumptions your costs would be:


	1 year		3 years
Service Class	$	111	$	347

* * *

Transamerica PineBridge Inflation Opportunities VP

Effective as of August 28, 2020, the portfolio will lower its management and sub-advisory fee schedules as described below.

The “Annual Fund Operating Expenses” table included in the “Fees and Expenses” section of the Prospectus and Summary Prospectus is deleted entirely and replaced with the following:


Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Class	Initial			Service
Management fees¹		0.49	%		0.49	%
Distribution and service (12b-1) fees		0.00	%		0.25	%
Other expenses		0.07	%		0.07	%
Total annual fund operating expenses		0.56	%		0.81	%

¹

Management fees have been restated to reflect a reduction in management fees effective August 28, 2020.

The “Example” table included in the Prospectus and Summary Prospectus is deleted entirely and replaced with the following:

Example: This Example is intended to help you compare the cost of investing in the portfolio with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the portfolio for the time periods indicated and then redeem all shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the portfolio’s operating expenses remain the same. The Example does not reflect charges that are, or may be, imposed under your variable life insurance policy or variable annuity contract. If such charges were reflected, costs would be higher. Although your actual costs may be higher or lower, based on these assumptions your costs would be:


	1 year		3 years		5 years		10 years
Initial Class	$	57	$	179	$	313	$	701
Service Class	$	83	$	259	$	450	$	1,002

* * *

Investors Should Retain this Supplement for Future Reference

June 22, 2020

Risk/Return:

rr_RiskReturnAbstract

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other expenses and acquired fund fees and expenses are based on estimates for the current fiscal year.

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

Management fees have been restated to reflect a reduction in management fees effective August 28, 2020.

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the portfolio with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the portfolio for the time periods indicated and then redeem all shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the portfolio’s operating expenses remain the same. The Example does not reflect charges that are, or may be, imposed under your variable life insurance policy or variable annuity contract. If such charges were reflected, costs would be higher. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Risk/Return:

rr_RiskReturnAbstract

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.70%

^[2]

1 year

rr_ExpenseExampleYear01

$ 111

Supplement to Prospectus [Text Block]

rr_SupplementToProspectusTextBlock

TRANSAMERICA SERIES TRUST

Supplement to the Currently Effective Prospectus, Summary Prospectuses

and Statement of Additional Information

* * *

Transamerica PineBridge Inflation Opportunities VP

* * *

Transamerica PineBridge Inflation Opportunities VP

Effective as of August 28, 2020, the portfolio will lower its management and sub-advisory fee schedules as described below.

The “Annual Fund Operating Expenses” table included in the “Fees and Expenses” section of the Prospectus and Summary Prospectus is deleted entirely and replaced with the following:


Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Class	Initial			Service
Management fees¹		0.49	%		0.49	%
Distribution and service (12b-1) fees		0.00	%		0.25	%
Other expenses		0.07	%		0.07	%
Total annual fund operating expenses		0.56	%		0.81	%

¹

Management fees have been restated to reflect a reduction in management fees effective August 28, 2020.

The “Example” table included in the Prospectus and Summary Prospectus is deleted entirely and replaced with the following:

Example: This Example is intended to help you compare the cost of investing in the portfolio with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the portfolio for the time periods indicated and then redeem all shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the portfolio’s operating expenses remain the same. The Example does not reflect charges that are, or may be, imposed under your variable life insurance policy or variable annuity contract. If such charges were reflected, costs would be higher. Although your actual costs may be higher or lower, based on these assumptions your costs would be:


	1 year		3 years		5 years		10 years
Initial Class	$	57	$	179	$	313	$	701
Service Class	$	83	$	259	$	450	$	1,002

* * *

Investors Should Retain this Supplement for Future Reference

June 22, 2020

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

Management fees have been restated to reflect a reduction in management fees effective August 28, 2020.

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the portfolio with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the portfolio for the time periods indicated and then redeem all shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the portfolio’s operating expenses remain the same. The Example does not reflect charges that are, or may be, imposed under your variable life insurance policy or variable annuity contract. If such charges were reflected, costs would be higher. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Risk/Return:

rr_RiskReturnAbstract

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Total annual fund operating expenses

rr_ExpensesOverAssets

0.56%

3 years

rr_ExpenseExampleYear03

179

10 years